Image reading device and image forming apparatus therewith

An image reading device has a document placement stage, a light source unit, and a sensor unit. The light source unit has a first light source part having a first light source at one end in the main scanning direction and a first light guide, a second light source part having a second light source at the other end in the main scanning direction and a second light guide, a first board where the first light source is mounted, and a second board where the second light source is mounted. The first and second boards each have a board base, a mounting part where the first or second light source is mounted, and a reflection face formed next to the first or second light source. The reflection faces of the first and second board faces face, to overlap the facing faces of the second and first light guides.