In this tyre managing apparatus, with regard to respective tyres, the back-and-forth force and the lateral force which are added to each of tyres are calculated based on the distances which are distance between each tyre and the center of gravity in the back-and-forth direction, the inertia moment of the vehicle, the vehicle weight of the vehicle, and the loads added to each of the tyres, which are as specification data of the vehicle, and based on the longitudinal acceleration, the lateral acceleration, and the yew angle acceleration, which are as state quantities of the vehicle. Also, the calculated results are memorized in the transponders of corresponding tyres.