To provide a collision safety structure of a cab vehicle of a simple structure capable of securing a living space by limiting moving quantity of a cab in a cab vehicle, especially a double cab vehicle when external force is applied, and of easily improving and adjusting impact energy absorption quantity of the vehicle.

Between a center mount rail 3 and a rear mount rail 4 disposed on a lower surface of a floor panel 6 of a double cab 7 mounted on a side member and the side member 2, a stopper member 1 to be fixed on a side of the side member 2 is provided. Move of the double cab 7 when external force is applied can be limited by the stopper member 1, and to the whole body of a vehicle, EA quantity corresponding to flexibility characteristics of the stopper member 1 is generated.