In a message authentication system in which a message is transmitted from a message transmission apparatus 100 to individual message reception apparatuses 120 through wireless communication connecting the message transmission apparatus 100 with the message reception apparatuses 120 via intermediary message reception apparatuses and the message is authenticated at each message reception apparatus, the message transmission apparatus first transmits an electronic signature to each message reception apparatus as a message transmission notification and then transmits the message and an authentication key to the message reception apparatus after allowing a predetermined time lag. Thus, the message reception apparatus does not need to hold the message before the authentication key is published (FIG. 7).