An optical scanner includes a scanning unit having a reflecting surface that reflects a laser beam and scans the laser beam in a primary scanning direction, a laser beam radiation unit that radiates laser beams to the reflecting surface from directions at predetermined angles to a reference plane, which is orthogonal to the reflecting surface and extending along the primary scanning direction, and optical members provided on optical paths of the laser beams after reflections. The laser beam radiation unit radiates the laser beams, in such a manner that, an angle on a plane orthogonal to the reference plane between a first and second optical paths is larger than an angle between the first and third optical paths, the second and third optical paths being adjacent to one side and other side of the first optical path, respectively. The optical member on the second optical path is nearer the reflecting surface than the third optical path.