A method of transmitting images in a subject to an outside of the subject using a wireless signal is provided. The method including: (a) transmitting to the outside of the subject a first signal corresponding to a first image obtained using a first imaging device, by timing on a first illumination device for illuminating the subject to capture the first image of the subject; (b) transmitting to the outside of the subject a second signal corresponding to a second image obtained using a second imaging device, by turning on a second illumination device for illuminating the subject to capture the second image of the subject; and (c) repeating (a) and (b), where at least initiation of the transmitting the first signal and initiation of the transmitting the second signals is alternately performed and the first and second illumination devices are alternately turned on coincidentally with transmission periods of the first and second signals, respectively.