An apparatus for mounting a seat belt to a vehicle body, may include a wire integrally having on a first end thereof a belt insert ring, an end of the seat belt being inserted into the belt insert ring, a wire installing unit coupled to a second end of the wire and secured to the vehicle body, and a belt restraining unit coupled to the vehicle body while slidably receiving the seat belt so as to restrain movement of the seat belt which may be inserted into the belt insert ring.