A feeder for use in a sheet-feed printing machine, in which, while a pile board (3)loaded with a paper sheet pile through a pallet (4) is moved up, paper sheets are fed to the printing unit through a side register lay, comprising a sensor (49,50) movable along a threaded shaft (33) according to the rotation of the threaded shaft to detect a side edge of the paper sheet pile, which is moved over the distance in the cross direction between a position at which the paper sheet pile is to be positioned when a left-pulling side register lay is used and a position at which the paper sheet pile is to be positioned when a right-pulling side register lay is used, and further comprising a non-stop device to insert another paper sheet pile under the paper sheet pile, or detecting means to detect the remaining amount of paper sheets and the top surface of the paper sheet pile.