A workpiece simulation part estimates the amount of movement of the workpiece from drive information and estimates the current position of the workpiece by adding the amount of movement to the previous position of the workpiece, the drive information being generated for, among at least one actuator, an actuator that is assumed to constrain the workpiece under the constraint conditions. A sensor simulation part uses the current position of the workpiece to generate sensor simulation information. An input/output switching part transmits the drive information to the workpiece simulation part and transmits the sensor simulation information as alternate information of the sensor information to the control-program execution part.