A communication device includes a receiver, a transmitter and an interruption module. The receiver receives an allocation signal indicating a first period usable by the communication device and a second period usable by a plurality of communication devices including the communication device. The transmitter transmits a transmission signal in the first period. If the transmission of the transmission signal is completed within the first period, the interruption module interrupts at least a part of power supply to the receiver in the second period. If the transmission of the transmission signal is not completed within the first period and directivity of radio waves used by a second communication device includes a direction of the communication device in a communication period allocated before the second period, the transmitter transmits the transmission signal in the second period.