An optical unit includes: an objective lens unit arranged on a distal end side; an image pickup unit arranged on a proximal end side of the objective lens unit; an optical frame; an image pickup device frame; a proximal-end-side outer circumferential face provided on a proximal end side of the optical frame; an inner circumferential face of a distal-end-side frame body provided on a distal end side of the image pickup device frame; a plurality of notches provided apart in a circumferential direction on an outer circumferential face of one of the frames, the plurality of notches having opening portions on end faces where the optical frame and the image pickup device frame face each other; and holding portions provided on an outer circumferential face of the other frame different from the one frame, the holding portions passing through the opening portions and being accommodated in the notches.