An optical scanner includes a plurality of automatic cleaning units which automatically cleans dust-proof glasses. The automatic cleaning units include screw shafts threadedly coupled to holding units that hold cleaning members. When the holding members are moved by rotationally driving the screw shafts of the automatic cleaning units at the same time, the height of the cleaning member of at least one of the automatic cleaning units with respect to the dust-proof glasses becomes different from the height of the cleaning members of the remaining automatic cleaning units with respect to the dust-proof glasses.