Provided is an imaging device including a lens mounting portion, which is a portion on which or from which an interchangeable lens is mountable or removable, an imaging element, and an optical system provided in a light path between the interchangeable lens and the imaging element in a state in which the interchangeable lens is mounted on the lens mounting portion. The optical system is disposed at a first position at which an image of a light flux from the optical system is formed on the imaging element at a position in the light path between the interchangeable lens and the imaging element, and is moved to a second position, which is different from the first position from the first position in association with an operation of removing the interchangeable lens from the lens mounting portion.