In the power save mode of an IEEE 802.11 adhoc network, a packet loss occurs unless the power save state of a receiving side is detected, failing in communication. However, there is no explicit notification on joining/leaving in/from a network, and it is difficult to detect and manage the state of a partner, including the detection timing. To solve this problem, a terminal always transmits an information notification packet (ATIM packet) in a time during which all terminals can receive it, prior to data transmission regardless of the power save state of a partner. With this mechanism, the terminal also explicitly notifies the partner of a change in the power save state of the terminal.