A differential mounting structure includes a pipe into which a bushing coupled to the differential is forcibly inserted. The pipe is inserted into a through hole of a cross member and is fixedly attached at one end thereof to a flange. Coupling bolts penetrating the flange are connected to nuts welded to the cross member. When the bushing used for installing the differential to the vehicle body is worn down and can no longer do its job, only the bushing mounting assembly is replaced or repaired in the present invention.