The present disclosure provides a signal transmission apparatus for transmitting a signal to a signal processing section provided inside a rotated rotary body, the signal transmission apparatus including: a waveguide tube provided on the rotating shaft of the rotary body; a signal transmitting section provided outside the rotary body to serve as a section for transmitting the signal through the waveguide tube; a signal receiving section provided inside the rotary body to serve as a section for receiving the signal transmitted by the signal transmitting section through the waveguide tube and supplying the signal to the signal processing section; a slip ring rotated along with the rotary body around the waveguide tube serving as a rotation axis; and a power supplying section provided outside the rotary body to serve as a section for supplying power to the signal processing section through the slip ring.