The relay apparatus comprises the matrix switch 61 and the CPU 62 to which control data are supplied from input devices. The CPU 62 detects whether it is possible to change the state of the specified electronic device according to the control data and controls transmission of the control data to the specified electronic device according to the result of the detection. The control data comprises change control data and reference control data for requesting the state of the selected electronic device to be changed and to be referred, respectively. In other words, the CPU 62 controls the matrix switch 61 so that both the change control data and the reference control data are transmitted to the selected electronic device when it is detected to be possible to change the state of the specified electronic device with control data and only the reference control data is transmitted to the specified electronic device when it is detected to be impossible to change the state of the selected electronic device.