Two mirrors (15) and (16) making an angle of 90 degrees are formed on a front face of a mirror member (17). An optical fiber for input (12) and an optical fiber for output (13) are held in a fiber array (14) with a predetermined interval, and an emission lens (23) and an injection lens (24) are provided on a front face of the fiber array (14) in a way that they are opposed to end faces of the optical fiber for input (12) and the optical fiber for output (13) respectively. According to the variable optical attenuator, when the mirror member (17) is straightly moved by an actuator (18), light attenuation can be varied thereby.