In a notification system for communicating between a sender cellular phone possessed by a sending person and a receiver cellular phone possessed by a receiving person, the sender cellular phone, which is possessed by the sending person who wants to communicate with the receiving person, is allowed to transmit an ON state indication signal indicating to switch a main power source to be in an ON state through a radio wave to the receiver cellular phone being in an OFF state. Thus, a main power source of the receiver cellular phone can be remotely turned ON.