A tire inflation pressure sensing apparatus includes a transmitter provided on a wheel of a vehicle and a receiver provided on a body of the vehicle. The transmitter includes a pressure sensor working to generate a pressure signal and a charging unit configured to be charged with electrical power via a radio wave from the receiver. The transmitter is configured to be triggered to send out the pressure signal by a change of operation of the receiver from an ON-mode, in which the receiver sends out the radio wave, to an OFF-mode in which that stops sending out the radio wave. The receiver works to change the operation thereof alternately between the ON-mode and OFF-mode in accordance with predefined processes, so that reliable transmissions of both the radio wave and the pressure signal between the transmitter and receiver are ensured without determining the relative position of the transmitter and receiver.