A tire valve unit is secured to a securing hole provided in a rim of a wheel of a vehicle. The tire valve unit includes a tire valve and a tire sensor. The tire valve includes a valve stem and an elastic cylindrical member encompassing the valve stem. The elastic cylindrical member has an annular securing groove in an outer circumferential surface of the elastic cylindrical member. A portion of the rim around the securing groove is fitted in the securing groove when the elastic cylindrical member is passed through the securing hole. The tire sensor is fixed to the valve stem. The tire sensor is arranged in the interior of a tire attached to the rim and capable of detecting the condition of the tire when the tire valve unit is secured to the rim. The elastic cylindrical member defines an annular space around the valve stem. The annular space extends from a position corresponding to the securing groove in an axial direction of the valve stem to communicate with the interior of the tire.