Provided is an auxiliary apparatus for a golf putter including a coupling member detachably coupled to a shaft of the golf putter and a guide light emitting device coupled to the coupling member and configured to emit a guide light to help golf putting. The coupling member includes a first coupling member opened at upper and lower portions and one side thereof and detachably coupled to the golf putter through the opened space, and a second coupling member extending from the first coupling member and opened at upper and lower portions thereof, the second coupling member being configured to accommodate the guide light emitting device through the opened space.