A user communicates with a companion with his or her portable telephone attached to a telephone attachment pocket of a robot. The robot acts in accordance with a voice signal which is outputted from the portable telephone, thereby behaving as if it were speaking to the user. The robot outputs a voice in response to the user's voice which is picked up by a microphone, thereby behaving as if it were listening to the user. Owing to this robot or a robot system using the same, the user feels less odd in his or her communication using the portable telephone.