To provide a transmitting apparatus, a receiving apparatus, and an in-vivo information acquiring system that enable to acquire image information corresponding to one image, by assuredly synchronizing between a capsule endoscope and the receiving apparatus. According to the present invention, a capsule endoscope 2 that transmits a radio signal including at least an image signal S to the receiving apparatus includes a signal processor 12 that outputs the image signal S, a reference signal generator 24 that generates a reference signal including a different signal level and outputs a reference signal component D including at least the reference signal, an inserting unit 14 that inserts the reference signal component D into a predetermined heading period of the image signal S and at least a portion of a blanking period in which a signal component does not exist, and a transmitting unit 15 that wirelessly transmits the image signal S output from the inserting unit 14 to an outside.