A batteryless tire inflation pressure detecting apparatus includes, on the body of a vehicle, antennas and a transmitter transmitting radio waves through the antennas. The apparatus also includes, on each wheel of the vehicle, a pressure sensor sensing the pressure of a tire, a transceiver, and a charging unit powering the pressure sensor and the transceiver. The charging unit is charged with electric power induced by a corresponding one of the radio waves received by the transceiver. The apparatus further includes, on the body of the vehicle, a receiver receiving pressure signals transmitted by the transceivers, a pressure determiner determining the pressures of the tires based on the pressure signals, and a controller. To minimize influence of the radio waves on neighboring devices, the controller controls the transmitter so that least two of the radio waves are transmitted at different times, or at the same with a phase difference therebetween.