A master apparatus generates a frame encryption key by using a session ID unique to communication with a slave apparatus, and an apparatus common key common to the master apparatus and the slave apparatus, encrypts data of an encryption part of an action frame by using the frame encryption key, and transmits, by broadcast, the action frame including the encryption part. Upon receiving the action frame, the slave apparatus transmits a participation request to the master apparatus, and participates in the network of the master apparatus. Then, the master apparatus and the slave apparatus execute a communication application.