An object of the present invention is to enable a receiving side to easily recognize which of imaging devices has picked up received image data. A capsule endoscope (one example of the in-vivo image acquiring apparatus) of the present invention is swallowed by a subject, and picks up images of the inside of organs of the subject. The capsule endoscope has a plurality of LEDs, a plurality of CCDs, and a transmission module. The CCDs paired with the LEDs pick up images of the inside of a body cavity illuminated by the LEDs. The transmission module adds identification data for identifying the CCDs to image data in front and rear directions of the capsule endoscope picked up by the CCDS, and transmit the image data together with the identification data to the receiving side.