To provide a feeder for feeding a plate-like workpiece to a working machine which is capable of outputting information on the change in thickness of the workpiece on the real time basis.

The feeder includes a frame, and a holding and conveying means which is supported by the frame to hold and convey workpieces so as to continuously feed the plate-like workpieces to a working machine. The holding and conveying means has a pressure detector for outputting the signal according to the pressure to be changed according to the thickness of the workpieces when the holding and conveying means is operated to hold the workpieces.