Abstract: A controller unit is made so that a work machine can be remotely controlled in a reliable manner irrespectively of whether the controller unit is used outdoors or indoors. Inside the controller unit 10 is provided a transmitter 11 that inputs a control signal S0 indicating the control content, converts the input control signal S0 to a radio signal Se and radio-transmits it toward the work machine 13. The work machine 13 operates according to the radio signal Se radio-transmitted from the transmitter 11. Meanwhile, a transmitter 12 similar to the internal transmitter 11 is provided externally to the controller unit 10. Thereupon, when the external transmitter 12 is connected to the controller unit 10, it is determined by a determining unit 14 inside the controller unit 10 that the external transmitter 12 is connected to the controller unit 10.