To reduce the workload of a user for setting a value of a variable for determining the direction of a tool at a target position and furthermore to reduce the movement time of a robot.

When a user sets a rotational angle of the tool around a predetermined axis as an optional variable, a controller sets the rotational angle around the predetermined axis as the optional variable settable to an optional value by the controller side. The controller sets an evaluation index which is based on the movement time required when a leading end of the tool moves from the present position to the target position and a positional error of the leading end of the tool after movement in relation to the target position, and determines the value of the optional variable by optimizing the evaluation index. Since each of the above processing is executed by the controller, the direction of the tool at the target position is automatically determined to a direction for minimizing the movement time of the robot.