To solve the problem of being troublesome work, due to requiring to periodically replenish air, since air of a tire naturally deflates.

A piston (2), an air supply pipe (6), an intake valve (9), a safety valve (10) and a cover (13) are arranged in a cylinder (1). A support shaft (12) is arranged on the piston (2), and a pusher (3) is arranged on the support shaft (12), and a weight (4) is arranged in the pusher (3). A spring (5) is arranged between the cover (13) and the pusher (3). The cylinder (1) can be fixed in the radial direction of a wheel, and the air supply pipe (6) is connected to an air supply port of the tire. The tire inflator is provided wherein when the tire rotates, the weight (4) pushes in the piston (2) by centrifugal force, and supplies air to the tire, and when rotation stops, the spring (5) extends, and pushes back the piston (2), and supplies the air in the cylinder.