My aims in this thesis are to establish how evidentiality is grammatically encoded in Korean, and to investigate the semantic nature of evidential morphemes in Korean, which helps us to explain the semantic and pragmatic behavior of evidential markers in non-declarative sentences, such as interrogatives. By doing so, this thesis also shows the implications of Korean evidentials to cross-linguistic studies on evidentiality, and the semantics and pragmatics of interrogatives in general. This thesis is organized as follows. Chapter 1 is a general introduction to evidentiality. In this chapter I distinguish narrow evidentiality (evidentiality is expressed via a set of distinguished morphemes) from the broad evidentiality (evidentiality is expressed via linguistic objects whose main function is not directly related to evidentiality), and delimit the main issues that I will discuss in this thesis. Here I also outline two of previous approaches to evidentiality in formal semantics, that is, to analyze evidentials as epistemic modals triggering evidential presuppositions, and to analyze evidentials as illocutionary operators introducing evidentiality as illocutionary forces. Then I introduce the background theory I will adopt, that is, Kaplan's (1989) theory of indexicals. Finally, I briefly outline the question I will mainly address in this thesis, that is, the evidential perspective shift in interrogatives. In Chapter 2 I argue that Korean is one of languages exhibiting the narrow evidentiality, and specifically, that Korean has (at least) two different evidential morphemes, the direct/perceptive--"te"--and the indirect/reportative--"ta"--. Especially I focus on the indirect/reportative--"ta"--since, while there is a consensus that Korean--"te"--is a direct evidential morpheme (or, at least, that--"te"--is related to the direct evidentiality, either in the broad sense or in the narrow sense), it is still on debate whether Korean also has an indirect/reportative evidential marker, or there is only a phonological contraction of a indirect quotation which introduces the implication similar to that of reportative evidentials. Based on a set of semantic and morphological diagnostics, I argue that non-final--"ta"--in Korean is truly a reportative evidential marker in Korean. While doing so, I also argue against several previous works which identify different morphemes as reportative evidential marker in Korean. Finally I will argue that Korean--"te"--should be analyzed as direct evidential marker, and even though it introduces implications which are similar to that of past-tense markers, it should not be analyzed as past tense marker. Chapter 3 concerns the semantic nature of Korean evidential markers. First I argue that evidential implications triggered by Korean--"te"--and--"ta"--are presuppositions, and not illocutionary forces, and in this sense, Korean evidentials behave in parallel with evidentials in languages like Turkish, Bulgarian, Norwegian and Stat'imcets, where evidentials markers are epistemic modals introducing evidential presuppositions. However, I also argue that, unlike Lee J.'s (2010) proposal, there is not enough evidence supporting the claim that Korean evidentials are epistemic modals, and that unlike languages where evidentials are epistemic modals, Korean evidentials do not have any semantic component of epistemic modals in their assertive meaning, but only trigger evidential presuppositions. This amounts to claiming that, typologically, Korean is a language which does not fit to any of the previous classifications: its evidentials are neither epistemic modals nor illocutionary operators, but merely presupposition triggers. Chapter 4 consists in the main proposal of this thesis. Here I introduce the puzzle of the evidential perspective shift in questions: evidentials are interpreted from speaker's perspective in declaratives, but they are expected to be interpreted from addressee's perspective in questions. Then I overview the background theories I am adopting here, that is, the semantics of indexicals proposed by Kaplan (1989) and the semantics of questions proposed by Hamblin (1973). Given this, I propose that Korean evidentials are functions from propositions to characters, introducing evidential presuppositions, and then I show that with this proposal we can derive the evidential perspective shift as a consequence of the interaction of the meaning of questions and the meaning of evidentials. Here I also show the advantages of this view over previous accounts developed in terms of pragmatics, and the differences between evidentials and other perspective-dependent components, like speaker-oriented adverbials and expressives. Furthermore, I discuss the implications of the analysis proposed for the semantics of interrogatives and of evidentiality in general. Chapter 5 is the conclusion of this thesis. Here I summarize the thesis, and address several remaining questions. 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