This paper deals with theoretical stability analysis and experimental study of flow-induced vibration of a flexible disk subjected to swirling fluid flow in a confined fluid. In the theoretical stability analysis, the basic equations of the swirling fluid flow around the flexible disk are based on the Navier-Stokes equations. The structural equation of the flexible disk is based on the Kirchhoff-Love's plate model. As a result, it is clarified that the flexible disk subjected to swirling fluid flow undertakes flow-induced vibration. The critical rotational speed at which the unstable vibration occurs and vibration modes are clarified theoretically and experimentally.