To provide a technique capable of reducing the size of an imaging device which can perform composition both by live-view and an optical finder while avoiding drop of light quantity in the optical finder.

The imaging device 1 includes a finder optical system which can guide an observation luminous flux from an imaging optical system, which is reflected by a main reflective surface 6a, to a finder window 10; and an imaging element 7 which receives the observation luminous flux and generates an image signal. A reflecting surface 68e that is one reflecting surface of a plurality of reflection surfaces included in a pentagonal mirror 58 of the finder optical system can be changed in reflection angle of the observation luminous flux. The course of the observation luminous reflected by the reflecting surface 68e is switched between a first optical path from the reflecting surface 68e to the finder window 10 and a second optical path PB from the reflecting surface 68e to the imaging element 7.