PURPOSE: To enable smooth intermittent rotation and reciprocating movement of an arm for changing a tool, by providing a turret for revolving and forward and backward movement which is engaged with a cam for revolving and for ward and backward movement and intermittently rotated in linkage with linear reciprocaing movement.

CONSTITUTION: A pair of first and second cams 7 and 8 for revolution, extended in a direction extending at right angles with a first drive shaft 3, are disposed in a position, where a tarret 6 for revolution is nipped therebetween, to rotate the tarret. First and second cams 18 and 19 for forward and backward move ment are disposed in a position, where a tarret 17 for forward and backward movement is nipped therebetween, to rotate the turret, and the cams 18 and 19 for forward and backward movement are securely mounted to a slider 10. In a housing 1, a first drive shaft 3 of an arm 2 for changing a tool is axially slidably spline-coupled with a cylinder shaft 5 rotatably supported through a bearing 4. A drive shaft 15 of a pinion 14 geared with a rack 13 is roatably supported to the housing 1 through a bearing 16.