PURPOSE: To automate screwing operation or the like of a caster, and to enhance the efficiency of operation by providing both a chuck part for insertedly holding and turning a first screw member and a table which is intermittently turned so as to feed a second screw member onto the first screw member, and which is lowered in interlock with the rotation of the chuck part at the time of screw tightening.

CONSTITUTION: When a clamp arm 62 is started to move back, a rotary cylinder 122 is operated to lower a stopper 123, and a table 10 is intermittently turned by a motor 116 to feed a leg part 2. After the position of a female screw part 8 has been confirmed by proximity switch 124, the rotation of the table 10 is stopped. Then, a chuck 3 is turned, and a cylinder 93 is operated to lower the table 10, and the tightening of a caster 1 is started, and after confirmation of the tightening amount by an optical sensor 37, and directly before the completion of tightening, while changing over the rotation of a rotating body 18 from a high speed to a low speed, tightening is carried out gradually. After the stopper 123 is lifted to complete tightening, the chuck 3 is opened, and also it is turned to the caster 1 taking-out position, and the caster 1 is taken out together with the leg.