PURPOSE: To bring a measuring point of a printed circuit board into contact with an electrode accurately with a simple construction by releasing the retention through a guide shaft to let the weight fall with a holding member lowered to hold the printed circuit board.

CONSTITUTION: As a holding member is lowered with an air cylinder and a pin of the holding member reaches a circuit board, a regulating member 27 of a guide shaft 26 gets in contact with a mobile member 55. This rotates the member 55 and rotating shafts 45 and 46 to release weights 49 and 50 from the retention by retaining members 53 and 54 of stopper members 51 and 52 and lets the weights fall by own gravity to hit the guide shafts 25 and 26. Then, the impact vibration propagates to promote contact with a simple construction thereby securing the contact between a measuring point of a printed circuit board and an electrode.