PURPOSE: To automatically push in a retaining pin into a housing tube and improve productivity by sliding the retaining pin which is pushed out of a feeder in a chute and, then holding the pin by means of the hands of a pin driving member and pushing the pin into the housing tube by means of a push rod.

CONSTITUTION: Retaining pins 3 which are not surely supported by a pin feeder 13 are shaken off by oscillating a housing case 11 with a push rod 16. Then, the pin 3 is pushed out from the feeder 13 into a chute 18 by means of a push- out device 17 and slides by its own weight in the chute 18 to be fed between the fingers 23a, 23a of the arms 23, 23 of a pin driving member 21. In this condition, the retaining hole of the housing tube 1 is opposed to the pin 3 and the tube 1 is installed on the housing tube supporting board 27. Then, as the push rod 26 is lowered by means of a push-out cylinder 28, the fingers 23a, 23a are gradually spread so as to be mutually separated and a pressing face 26a is brought into contact with the base portion 3b of the pin 3 to press the pin 3 into the housing tube 1.