A technique is provided which can improve optical characteristics by suppressing the occurrence of an error in attachment of a rotary deflector that deflects a light flux from a light source and scans it in a main scanning direction. There are provided a rotary deflector that deflects the light flux from the light source and scans it in the main scanning direction, an imaging optical system that images the light flux scanned by the rotary deflector onto a specified scanning object, a support part that supports the rotary deflector rotatably, and a positioning part that comes in contact with the support part at plural contact positions and positions the support part, in which a shortest distance between the plural contact positions in an optical axis direction of the imaging optical system is longer than a shortest distance between the plural contact positions in the main scanning direction.