A capsule endoscope 3 is inserted into a subject and transmits a capsule ID, which is received by an RF receiving unit 11 of a receiving apparatus 2. A capsule ID detecting circuit 19 detects the capsule ID. A control unit C recognizes a type of the capsule endoscope 3 based on the detected capsule ID, and changes over a threshold of received field strength of a receiving antenna. Thus, a content of processing for the capsule endoscope 3 is changed over, and a selection controller C1 selects a receiving antenna for an image receiving period from receiving antennas A1 to An.