A viewer 4 as a compact display device displays a body cavity image picked up by a capsule endoscope 3. When a communication-cable connection detector 48 detects a communication cable connection between a receiving apparatus 2 and the viewer 4, a control unit 49 switch controls a changeover switch 44 based on this connection detection, thereby switching a display of an LCD 41 to a display of image data from wire. Next, information necessary for an examination such as image data is taken in from the receiving apparatus 2 via a communication cable 5, and is displayed in an LCD 41. With this arrangement, a display unit is not necessary in the receiving apparatus 2, and a circuit configuration becomes simple. The receiving apparatus can be made compact and light, and power consumption can be decreased.