PURPOSE: To quickly cope with a part jam and to smooth automatic mounting by disposing a part detection sensor on the inlet and outlet of a straight advancing feeder, and displaying the existence/absence of a jammed part in a display circuit.

CONSTITUTION: When a part is transferred by a lift 7 of a straight advancing feeder 6, the part is detected by sensors 11, 12 at the inlet and outlet, respectively. In this case, when the part is smoothly transferred, the part is detected by the sensors 11, 12 within the set time of a timer, and 'no jam' is displayed on a display device not shown. When the outlet sensor 11 does not detect a part within the set time, the display is put out as a part jam, and an alarm is given. In this arrangement, a part jam can be quickly coped with, and automatic mounting is smoothed.