A coupling controller that performs coupling control of a device with a bus includes a decision circuit configured to decide whether a voltage level of a signal inputted from each of a plurality of signal lines included in the bus is lower than a given threshold value, and a switching controller configured to perform switching control for a switching unit, which is interposed between the bus and the device and switches coupling between each of the plurality of signal lines and the device, such that the signal line with regard to which it is decided by the decision circuit that the voltage level of the signal is lower than the given threshold value is coupled with the device.