To finely adjust optical attenuation or its attenuation quantity by generating a gap between ferrules by the fine adjustment in the axial direction of the ferrules which is generated by the relative movement of a spring and a difference of pitches of the spring in the combination of an adjustable rotor and the ferrule.

The variable optical attenuator is provided with optical fiber holding structure, a combining rotor, a connection member, and a protection member. When the variable optical attenuator is engaged with a light source or an optical fiber connector plug, the combination of ferrules is linearly moved in the optical axis direction by rotating an adjustable rotor and a gap between the ferrule and the light source or the optical fiber plug is changed, so that optical intensity can be changed.