PURPOSE: To increase the operability remarkably by locating the changing device close to the electric discharge machine and by performing the work with full automation by remote control.

CONSTITUTION: The outer side shaft 33 is arranged with penetration at the center position of the inner side frame 32 and the inner side shaft 34 is arranged with penetration at the inner peripheral side thereof. A clipper 35 is set up over four places at the position corresponding to the hole formed on a rotary disc 11 on the inner side frame 32 and composed of a claw 36 and the air cylinder mechanism 37 to open and close the claw thereof. At the position corresponding to the fitting bolt of the rotary disc 11 of the inner side frame 32 the operation mechanism 41 for rotary disc fitting bolt is set up. This mechanism 41 is composed of a socket wrench 42, air cylinder 43, spline shaft 44 and nut runner 45. A cylinder chamber 51 is formed between the outer side shaft 33 and inner side shaft 34 and high pressure air is fed via air hose 52.