An imaging device includes: an imaging sensor; an optical system that changes an image magnification of a object image according to a position of a focus lens; and a controller that causes the imaging sensor to generate the plurality of pieces of image data by causing the imaging sensor to pick up the object image while moving the focus lens to generate still image data based on the plurality of pieces of image data. When generating the still image data, the controller finds an entrance pupil position of the optical system based on the position of the focus lens for each of the plurality of pieces of image data, and calculates an image magnification change rate indicating a change of the image magnification of the object image based on the found entrance pupil position, magnifies each of the plurality of pieces of image data such that a size of the object image indicated by each of the plurality of pieces of image data becomes a predetermined size, based on the corresponding image magnification change rate, and synthesizes the plurality of pieces of magnified image data to generate the still image data.