To make the locking of an outside firmly fastening rope and the centering of an anti skid device to a tire easy and improve fitting performance.

In an antiskid device for tires, which is provided with an antiskid body 1 integrally molded of non-metallic material in a net state so that grid parts inclined in the cross direction are longitudinally continued to each other and an inextensional inside firmly fastening rope 3 mounted along the inside end edge 1A of this antiskid body 1, the natural length L1 in the developed state of the antiskid body 1 set to 93% to 99% of the peripheral length of a tire, and the length L2 of an inside firmly fastening rope 3 is set so that the displacement of the cross direction center of the antiskid body 1 to the cross direction center of the tire is within ±10 mm.