To provide an inexpensive optical attenuator capable of being attenuated highly precisely.

The optical attenuator varies optical transmission quantity between optical fibers by moving a light shield plate 30 between the ends of optical fibers F1 and F2 of which the incident and emitting optical axes are aligned. The actuator 31 for driving a light shield plate is composed of: a turning plate 32 which is formed as a unit with the light shield plate 30 which is arranged in a hole 22 of a substrate 21 and extended in the direction between the ends of both optical fibers; shafts 33 and 34 which support freely turnably the turning plate 32 by connecting the intermediate parts of the turning plate 32 and the internal edges of the substrate 21; and a driving means which moves froward and retracts the shield plate 30 between the front ends of the optical fibers by giving turning force on the other end of the turning plate 32.