A communication device communicates with another communication device via an information managing device. The communication device includes a transmitter unit, a storage unit, and a control unit. The transmitter unit transmits presence information to the other communication device via the information managing device. The storage unit stores a program. If the communication device executes the program, the control unit judges whether the presence information currently registered needs to be changed based on executing the program. If the control unit judges that the presence information currently registered needs to be changed, the control unit changes the presence information based on executing the program. The control unit controls the transmitter unit to transmit the changed presence information as updated presence information to the other communication device via the information managing device.