In a sheet counter in which sheets held in a stack in sheet-holding means are successively separated from the stack by suction heads, there are provided first electrical switch means such as a microswitch which is closed when the sheet-holding means has been manually moved to a sheet-loading position and second switch means which is closed when the stack of sheets loaded on the sheet-holding means has been carried to a counting position. An electric motor for imparting rotation to the suction heads and a vacuum pump for creating a partial vacuum therein are set in operation only when both of the first and second switch means have been thus closed. The sheet counter is also provided with means for properly readjusting the position of the suction heads relative to the stack of sheets prior to counting operation.