A control method for an optical transceiver includes interrupting internal repetitive internal processing in response to a command from a host apparatus and executing an interrupt process for transmitting monitoring data. The method sets a processing mode of the interrupt process to a first processing mode when a processing time necessary to execute the interrupt process and one cycle of the repetitive processing is shorter than a threshold value, and to a second processing mode when the processing time necessary to execute the interrupt process and one cycle of the repetitive processing is longer than the threshold value. In the first mode, the interrupt process stores first monitoring data read out from a memory unit in a transmission register, stops the stretching of a clock signal, and subsequently reads out second monitoring data from the memory unit to follow the first monitoring data. In the second mode, the interrupt process stores the first monitoring data read out from the memory unit in the transmission register, reads out the second monitoring data from the memory unit, and subsequently stops the stretching of the clock signal.