PURPOSE: To prevent both the slipping of a tire and the damage of a road surface by providing a spike in the inside of each groove formed on the ground- contacting surface of the tire so as to be oscillatable via a shaft and bearings, and so as to be retractable to the groove via a support plate.

CONSTITUTION: On the ground-contacting surface 9 of a tire, grooves 10 for preventing slipping on a snowless road surface, and also deeper grooves 1 are formed. And in the bottom part 2 of the groove 1, a shaft 4 of a spike 3 is oscillatably arranged via bearings 5. In the middle part of the groove 1, a support plate 6 for supporting the middle part of the spike 3 to prevent unnecessary idle movement is arranged, and also a magnetic attracting part 8 is arranged in the part opposite to the support plate 6. And as the tire slips, the support plate 6 is detached from the magnetic attracting part 8, and the spike 3 is projected from the inside of the groove 1 to the outside of the ground-contacting surface 9. Thus, the spike 3 is made to bit into an icy,. snowy road surface or the like for preventing the slipping of the tire.