A sender of a message can transmit a message to an unspecified user merely by specifying a condition of space without specifying a recipient of the message, using an information processing terminal transmitting a message not with a user address to specify a user but with an area address (a condition of space) to specify an area within an electric wave reachable range of a radio base station; and a server converting the area address to a user address which specifies a PHS terminal currently located in the area represented by said area address and transmitting the message with a converted address to a switching equipment.