PURPOSE: To prevent temperature rise and deformation of an original or the like without incurring a large sized projection section by controlling a lighting voltage of a lamp synchronously with the reciprocating operation of a scanning unit and controlling a time from the end of reciprocation to start of succeeding reciprocation.

CONSTITUTION: A read sensor reads an original while a scanning unit 113 moves in a main scanning direction A. The unit 113 restores to a home position for each main scanning by the movement in a direction B and a subscanning unit drive motor 11 moves a subscanning unit 4 in a direction C by only a distance corresponding to a read width. The subscanning unit 4 is returned in a direction D at the end of read of one original. Then a lighting voltage of a lamp lighting the transparent original is controlled synchronously with the reciprocating operation of the unit 113 to control the time from the end of reciprocation of the unit 113 till the start of succeeding reciprocation.