An optical device comprises: a first holding frame holding an optical system; a second holding frame holding the first holding frame and having a groove provided on a face opposing the first holding frame; an elastic member provided between the first holding frame and the second holding frame; a position determining portion capable of determining a position of the first holding frame towards the elastic member, and provided to sandwich, with the elastic member, the first holding frame; a fixing portion is capable of fixing the first holding frame towards the position determining portion so that the first holding frame is fixed, and which is provided to sandwich, with the position determining portion, the first holding frame; and a protruding portion which has a first end fixed to the first holding frame, and another end which differs from the first end and which is inserted into the groove.