To provide a snap-in valve capable of maintaining high operability associated with attachment to a rim and also maintaining a small tilt even if force accompanying rotary motion of the rim operates, and a tire valve unit mounted on the rim using the snap-in valve.

A tire valve 1 is mounted on a wheel of a vehicle to be inserted into a valve mounting hole Rh of a rim R. A tire sensor for detecting the state of the tire is connected to the inside of the rim R. The tire valve 1 has a cylindrical elastic member 16, increasing in outer diameter from the inside to the outside of the rim R, around a valve stem 12, and in the mounting state, a mounting groove 19 which has an outer diameter larger than the inner diameter of the valve mounting hole Rh comes into contact with an inner surface of the valve mounting hole Rh. A support part 12D which elastically deforms in response to compressive deformation of the cylindrical elastic member 16 and is pressed by the mounting groove 19 in the mounting state to apply force to the mounting groove 19 against the pressing is provided closer to a tip side than the mounting groove 19.