An optical scanner capable of achieving a optical scanning processing with higher speed and uniformity in pitches of scan light, while spacing saving and reduction in cost are attempted, is provided. An optical scanner comprising a plurality of the light sources that are allocated in positions different from one another in a sub-scanning direction orthogonal to the main-scanning direction, a pre-deflection optical system, and a polygon mirror that scans the light flux shaped in the pre-deflection optical system in the main-scanning direction by reflecting and deflecting the light flux by a plurality of reflecting surfaces arranged thereon corresponding to each of the plurality of photoconductors in a rotational direction, and an inclination angle of each of the plurality of reflecting surfaces with respect to a rotational axis of the polygon mirror is set to an angle depending on the photoconductor to which each of the reflecting surfaces corresponds.