PURPOSE: To enable the correct follow-up action of a robot even with the fluctuation of conveyor speed by setting acceleration at the time of accelerating the robot from the initial position up to the same speed as the moving speed of a workpiece on the basis of the moving speed of a conveyor in such a way that the accelerating delay quantity becomes the prespecified value.

CONSTITUTION: The moving speed of a conveyor 12 is detected by a speed detecting means 18. On the basis of the moving speed of the conveyor 12, an acceleration setting means 24 sets acceleration at the time of accelerating a robot 11 from the initial position up to the same speed as the moving speed of a workpiece 13 in such a way that the moving distance difference between the robot 11 and the workpiece 13 within an accelerating period, that is, the accelerating delay quantity, becomes the prespecified value. Accordingly, with the initial position of the robot 11 set into a position corresponding to the specified accelerating delay quantity, the acceleration of the robot 11 changes according to the moving speed of the conveyor 12 even if the moving speed of the conveyor 12 changes. Accordingly, when the accelerating ended, the robot 11 and the workpiece 13 positively have the specified position relation.