Using the framework of conversation analysis, this study investigated the interactional workings of laughter in task-based interactions. The analysis was drawn from 160 cases of pair work interactions, collected in 2nd-semester Japanese-as-a-foreign-language classrooms. The pair work activities examined in this study are mostly grammar-focused, with prescribed sequences of turns presented on activity prompts. While the learners are closely following these prescribed sequences, analysis of their laughter reveals the complex interplays of their interpretations of activity designs, their appropriation of instructional materials, their negotiation of moment-by-moment orientations, and their positioning in interpersonal relationships, all of which give rise to unique interactional outcomes. Moreover, the resourceful use of laughter can be deemed relevant to language learning as it relates to active engagement with language use. This study suggests that a close examination of laughter provides rich information about task-based interactions that may otherwise be overlooked.