A communication device includes a receiving circuit and a start-up time adjustment circuit configured to transmit, to the receiving circuit, a start signal that instructs a change from a sleep state to an active state, wherein the start-up time adjustment circuit is configured to transmit, to the receiving circuit, a first start signal that instructs a change from the sleep state to the active state at a first time earlier than a second time when a first signal reaches the communication device, measure a first time difference between the second time and the first time, determine, based on the first time difference, a third time when the receiving circuit is changed from the active state to the sleep state, and transmit a second start signal that instructs a change from the sleep state to the active state to the receiving circuit at the third time.