Interest in educational research can be categorised into situational interest (SI) and individual interest (II); the sequential phases of interest development for learning have long been recognised as triggered SI, maintained SI, emerging II, and well-developed II. This study proposes an interest development model which involves SI and II mentally developed during students' preparation for and participation in annual 'PowerTech' STEAM contests in Taiwan. In July 2015, data were first collected to examine students' triggered SI, and 4 months later in the world contest to examine the local contest winning students' maintained SI. Also, during the contest, data were collected on-site to examine the students' emerging II. Finally, the same measurement tool was administered again for the world contest winning students 2 months later in February 2016. The results of this study showed that triggered SI is positively related to maintained SI. Maintained SI is positively related to emerging II, but it is not significantly related to well-developed II. Emerging II is positively related to well-developed II. The implication of this finding is that a well-designed competition may raise students' SI so that emerging II and well-developed II could mature due to the effect of maintained SI.