Transmitter for tire condition monitoring apparatus and antenna for the transmitter

A transmitter for a tire condition monitoring apparatus includes a circuit board, circuit components mounted on a main surface of the circuit board, and a transmission antenna that transmits a transmission signal as radio waves. The transmission antenna includes a loop shaped transmission conductor that transmits radio waves. The transmission conductor has a loop plane that is substantially perpendicular to the main surface of the circuit board. When the transmitter is attached to the wheel, the loop plane is substantially perpendicular to a portion of the circumferential surface of the wheel that faces the transmitter. As a result, when the transmitter is attached to the wheel, the radio wave transmission efficiency is effectively prevented from being reduced.