To easily and surely connect both ends of an internal fastening cord of a tire slip preventing device, to increase the durability, and to reduce the manufacturing cost.

This internal connector 2 for the tire slip preventing device 1 is provided between the vehicle side end section of a joint strip 6 of a net body 3 and one end of the internal fastening cord 4, and engages the other end section of the internal fastening cord 4 with a hook member 12. The internal connector 2 for the tire slip preventing device 1 is equipped with a connector main body 13 having a notched section 18 in which the hook member 12 is inserted, a locking element 14 which is pivotally supported by the connector main body 13, and fastens the hook member 12 inserted in the notched section 18, a flexible operating member 16 one end of which is connected with the locking element 14, and turns the locking element 14 in the engaging/disengaging direction, and an urging means 15 which urges the locking element 14 in the fastening direction. On the locking element 14, a tilted section 22 for turning in the disengaging direction by the hook member 12 which is inserted in the notched section 18 is formed.