Transmitter unit and tire condition monitoring apparatus

A transmitter unit of an apparatus for monitoring the condition of a tire includes a casing (31) having an opening defined in an end of the casing. A transmitter (15) is received in the casing through the opening (33). The transmitter gathers and wirelessly transmits information regarding the condition of the tire. The casing (31) is secured to the outer circumferential surface of a rim wheel (17) of the tire by an adhesive tape (32) or an adhesive agent. Accordingly, the transmitter unit is capable of being attached to the rim wheel in a suitable manner.