Transmission and receiving of image data recorded on a digital still camera to and from a server are controlled by a portable telephone set. At the time of transmission, communication between the portable telephone set and the digital still camera and communication between the portable telephone set and the server are established. A reading command is issued from the portable telephone set to the camera. Image data are transmitted in packet units to the portable telephone set from the camera in response to the reading command. The image data is transmitted to the server from the portable telephone set. At the time of receiving, when the communication is established, all image data are transmitted to the portable telephone set from the server. All the image data are transmitted to the camera from the portable telephone set and are recorded in the camera. It is possible to control the transmission and receiving of the image data by the portable telephone set.