A structure for mounting a bearing bracket is provided. The structure includes a supporting portion into which a drive shaft is fitted and a coupling portion which is enlarged from the supporting portion and is fastened by bolts to a fixing portion formed at a power train. The coupling portion has two or more apertures into which the bolts are inserted, and at least one enlarged portion that protrudes on a surface, which comes into contact with the fixing portion, to enlarge a length of each apertures, and the fixing portion has bolt bore opened to correspond to the apertures of the coupling portion, respectively, and an enlarged groove formed at the bolt bore where the enlarged portion enters and has an increased diameter to fit the enlarged portion into the enlarged groove.