1. An imaging device that captures a subject, generates image data of the subject, captures a moving image, and captures a still image during moving image capturing including directly after moving image capturing end, the device comprising: a moving image special effect image processing unit that performs moving image special effect image processing of synthesizing captured image data with a plurality of image data captured before the image data at a predetermined ratio; and a control unit that changes the number of image data synthesized by the moving image special effect image processing unit depending on whether the captured image data is a moving image or a still image, wherein the earlier image data is captured in terms of time, the smaller the predetermined ratio is.