A communication device includes a communication circuit and circuitry. The communication circuit executes a function related to communication. The circuitry detects an input signal input to the communication circuit, transitions the communication device between a first power state, and a second power state in which the communication device consumes less power than in the first power state, and changes a clock frequency of the communication circuit. When the input signal is detected in the second power state of the communication device, the circuitry changes the clock frequency of the communication circuit while maintaining the second power state.