Abstract: An automatic tool change mechanism containing a cam shaft linked with a moter and a slotted cam. The cam shaft is driven by the motor to actuate the slotted cam to turn. The slotted cam is provided with a cam-profile groove, which is dimensioned so as to permit a driven roller to roll along the groove. The driven roller is caused to travel along the course of the cam-profile groove so as to cause an L-shaped rod to rock when the slotted cam is rotated by the cam shaft. The L-shaped rod is linked with a planetary gear, which engages a sector gear. The L-shaped rod contains a rocking section which actuates the planetary gear to turn. The planetary gear is connected with an output pitman, which is in turn coupled with a tool change shaft to cause the tool change shaft to engage in a linear motion. The driven roller also causes a turret, which is normal to the cam shaft, to rotate, and the rotation of the turret causes the tool change shaft to engage in a revolving motion.