PURPOSE: To reduce manhours in the preparation for replacement of parts while enhancing the operating rate and reliability of a mounter by a constitution wherein a signal including the information representative of the residual number of parts is transmitted to an automatically guided vehicle (AGV) from a parts cassette equipped with a memory and an AGV transfers supplementary parts to a parts replacing site upon receiving the signal.

CONSTITUTION: When a decision is made that the number of residual parts stored in a memory of a parts cassette 5 is lower than an arbitrary value, a mounter displays a message on a screen and lights an alarm lamp and a signal transmitting means disposed at the parts cassette 5 transmits information notifying runout of parts to the AGV. The AGV receives the information through a signal receiving means mounted thereon and loads the supplementary parts being transferred to a parts replacing site. A worker replaces the parts after the mounter stops due to run-out of parts.