To provide a semi-fixed type number stay for a number plate of a vehicle designed to run both on an ordinary road and a circuit capable of folding the number plate only when running on the circuit without removing the number plate, to cause a similar effect when the number plate is removed and maintaining a fixing method in conformity to the Road Traffic Law when the vehicle runs on the ordinary road so that it is possible to run on the ordinary road without changing anything by touching with hand.

A magnet for fixation (7) is adjusted up and down by a screw so that the fixation is loosened by wind pressure by any speed of cause the number plate to the folded, and thereby it is made possible to run both on the ordinary road and circuit.