Abstract: An optical device includes an impact position adjusting part which is an operation adjusting part. The impact position adjusting part includes a rotating operation part, a shaft part, a fixed tubular part which is a first tubular part formed with outer peripheral recesses-projections, and a rotating tubular part which is a second tubular part formed with inner peripheral recesses-projections. According to an operation of a user, the rotating operation part moves together with the rotating tubular part to a rotatable position at which the outer peripheral recesses-projections and the inner peripheral recesses-projections are separated, and a rotation prohibited position at which the outer peripheral recesses-projections and the inner peripheral recesses-projections are engaged. In a vicinity of an end part on a side close to the rotating tubular part, a width of a projection of the outer peripheral recesses-projections of the fixed tubular part gradually decreases toward the end part.