An optical unit includes a first barrel, a second barrel, a third barrel, and a position detection unit. Eight magnets including first and second magnets are fixed to the first barrel. A first and second coils are fixed to the second barrel. The position detection unit includes a magnetic sensor configured to detect magnetic fields generated by the first and second magnets and to generate a detection signal having a corresponding relation with a position of the first barrel. The third barrel includes a position defining surface parallel to a moving direction of the first barrel. The position detection unit is fixed to the position defining surface.