A relay device for being used in a medical device including a first device and a plurality of second devices (65, 24), the second devices (65, 24) each configured for performing control signal communication with the first device, and for relaying the control signal communication between the first device and the second devices (65, 24), the relay device comprising: a programmable logic device including: a first interface unit configured to communicate with the first device in a communication scheme corresponding to a communication scheme of the first device; and a plurality of second interface units (612, 613) each configured to perform communication with the respective second devices (65, 24) in communication schemes corresponding to communication schemes of the respective second devices (65, 24); and a plurality of pairs (615, 616; 617, 618) of a first storage unit and a second storage unit, wherein the pairs of the first storage unit (615, 617) and the second storage unit (616, 618) are provided to each of the respective second interface units (612, 613), the programmable logic device is configured to temporarily store a control signal received from the first device via the first interface unit in the first storage unit of a first of the pairs of first and second storage units at a first communication timing, and transmit the control signal to the respective second device via the respective second interface unit at a second communication timing, and temporarily store a control signal received from the said respective second device via the respective second interface unit in the second storage unit of the first of the pairs of the first and second storage units at a third communication timing, and transmit the control signal to the first device via the first interface unit at the first communication timing, and the first communication timing and the second and the third communication timings are set at timings shifted from one another. a programmable logic device including: a first interface unit configured to communicate with the first device in a communication scheme corresponding to a communication scheme of the first device; and a plurality of second interface units (612, 613) each configured to perform communication with the respective second devices (65, 24) in communication schemes corresponding to communication schemes of the respective second devices (65, 24); and a first interface unit configured to communicate with the first device in a communication scheme corresponding to a communication scheme of the first device; and a plurality of second interface units (612, 613) each configured to perform communication with the respective second devices (65, 24) in communication schemes corresponding to communication schemes of the respective second devices (65, 24); and a plurality of pairs (615, 616; 617, 618) of a first storage unit and a second storage unit, wherein the pairs of the first storage unit (615, 617) and the second storage unit (616, 618) are provided to each of the respective second interface units (612, 613), the programmable logic device is configured to temporarily store a control signal received from the first device via the first interface unit in the first storage unit of a first of the pairs of first and second storage units at a first communication timing, and transmit the control signal to the respective second device via the respective second interface unit at a second communication timing, and temporarily store a control signal received from the said respective second device via the respective second interface unit in the second storage unit of the first of the pairs of the first and second storage units at a third communication timing, and transmit the control signal to the first device via the first interface unit at the first communication timing, and temporarily store a control signal received from the first device via the first interface unit in the first storage unit of a first of the pairs of first and second storage units at a first communication timing, and transmit the control signal to the respective second device via the respective second interface unit at a second communication timing, and temporarily store a control signal received from the said respective second device via the respective second interface unit in the second storage unit of the first of the pairs of the first and second storage units at a third communication timing, and transmit the control signal to the first device via the first interface unit at the first communication timing, and the first communication timing and the second and the third communication timings are set at timings shifted from one another.