OPTICAL UNIT

PROBLEM TO BE SOLVED: To provide an optical unit capable of achieving the stability of an assembled state while improving assembly properties.SOLUTION: A third lens frame unit 70 comprises: a third front-side lens frame 73 having a first reference surface 73b; a third rear-side lens frame 74 having second reference surfaces 74d and 174d which abut on the first reference surface 73b; a third front-side lens group G3A mounted on the third front-side lens frame 73; a third rear-side lens group G3B mounted on the third rear-side lens frame 74; and a flat spring 72 which is mounted on the third front-side lens frame 73 and which presses the third rear-side lens frame 74 such that the second reference surfaces 74d and 174d are pressed to the first reference surface 73b.