A portable telephone set comprises a substrate part and a telephone set and an accessory device, which are attached to the substrate part. The substrate part includes a first connector connected with the telephone set, a second connector connected with the accessory device and a wiring part for connecting between these connectors. The accessory device is one or more of, for example, a display device with a speaker, a camera and a data communication device. Between a telephone set installation region and an accessory device installation region of the substrate part, a hinge part or a flexible member is disposed. Therefore, the portable telephone set can be folded.