An image capturing apparatus whose lens unit can be attached to and detached from a camera body section includes: an image-capturing signal processing section that generates an image signal by performing an image capturing process of subject light introduced via the lens unit; an attachment detecting section that generates a detection signal indicating whether or not the lens unit is attached to the camera body section; and a control section that determines whether or not the lens unit has been interchanged or detached and attached by using the detection signal, and performs a process of forming index data with respect to the image signal on the basis of a result of the determination.