Disclosed is a bracket for fixing a reducer in a fire sprinkler, the bracket including: a main body part provided with a cutaway seat for allowing the reducer to be seated therein; and a coupling part openably coupled with the main body part, formed with a groove at a side thereof to lock the reducer seated in the cutaway seat of the main body part, and configured to lock and release the reducer seated in the cutaway seat of the main body part by being opened and closed, wherein an edge of the cutaway seat of the main body part is provided with a main body part wing to increase a contact area with the reducer seated in the cutaway seat, and an edge of the groove of the coupling part is provided with a coupling part wing to increase the contact area with the reducer.