Abstract: An external antenna positioned external to a tire, and an internal antenna provided inside a valve of the tire, which transmits and receives power by electromagnetic waves in a predetermined high frequency band is substituted as a new source of power, for a tire pressure/temperature detection device that conventionally uses a battery power source. If the electromagnetic waves in a predetermined high frequency band are well matched to the physical structure and electrical structure of the tire, then, in the space between the tire and a wheel, a magnetic field component is distributed that is substantially perpendicular to the plane that includes the maximum diameter of tire. If the internal antenna is matched to the direction of maximum magnetic field reception, when the tire rotates, and when the position of the wheel is stopped, substantially stable power may be received.