A receiver includes an antenna unit that is able to receive a transmission signal from a subject alternately at different reception levels. A wave detection unit wave-detects the transmission signal to generate a detection signal. The detection signal has a signal level that becomes fixed in accordance with the transmission signal when the antenna unit receives the transmission signal at a reception level greater than or equal to a reception limit, and the signal level of the detection signal becomes non-fixed when the antenna unit receives the transmission signal at a reception level that is less than the reception limit. A correction unit removes, when the detection signal includes a fixed value session and a non-fixed value session, the non-fixed value session and corrects the signal level of the non-fixed value session to a level equivalent to the signal level of a fixed value session.