An apparatus for manufacturing a group III nitride single crystal comprising: a reaction vessel comprising a reaction area, wherein in the reaction area, a group III source gas and a nitrogen source gas are reacted such that a group III nitride crystal is grown on a substrate; a susceptor arranged in the reaction area and supporting the substrate; a group III source gas supply nozzle supplying the group III source gas to the reaction area; and a nitrogen source gas supply nozzle supplying the nitrogen source gas to the reaction area, wherein the nitrogen source gas supply nozzle is configured to supply the nitrogen source gas and at least one halogen-based gas selected from the group consisting of a hydrogen halide gas and a halogen gas to the reaction area, and wherein the nitrogen source gas supply nozzle comprises: a nitrogen source gas inlet from which the nitrogen source gas is introduced to the reaction vessel; a nitrogen source gas outlet from which the nitrogen source gas flows out to the reaction area; and a junction arranged between the nitrogen source gas inlet and the nitrogen source gas outlet, wherein a halogen-based gas inlet nozzle is joined to the nitrogen source gas supply nozzle at the junction, and wherein the halogen-based gas inlet nozzle supplies at least one halogen-based gas selected from a group consisting of a hydrogen halide gas and a halogen gas. a reaction vessel comprising a reaction area, wherein in the reaction area, a group III source gas and a nitrogen source gas are reacted such that a group III nitride crystal is grown on a substrate; a susceptor arranged in the reaction area and supporting the substrate; a group III source gas supply nozzle supplying the group III source gas to the reaction area; and a nitrogen source gas supply nozzle supplying the nitrogen source gas to the reaction area, wherein the nitrogen source gas supply nozzle is configured to supply the nitrogen source gas and at least one halogen-based gas selected from the group consisting of a hydrogen halide gas and a halogen gas to the reaction area, and wherein the nitrogen source gas supply nozzle comprises: a nitrogen source gas inlet from which the nitrogen source gas is introduced to the reaction vessel; a nitrogen source gas outlet from which the nitrogen source gas flows out to the reaction area; and a junction arranged between the nitrogen source gas inlet and the nitrogen source gas outlet, wherein a halogen-based gas inlet nozzle is joined to the nitrogen source gas supply nozzle at the junction, and wherein the halogen-based gas inlet nozzle supplies at least one halogen-based gas selected from a group consisting of a hydrogen halide gas and a halogen gas. a nitrogen source gas inlet from which the nitrogen source gas is introduced to the reaction vessel; a nitrogen source gas outlet from which the nitrogen source gas flows out to the reaction area; and a junction arranged between the nitrogen source gas inlet and the nitrogen source gas outlet, wherein a halogen-based gas inlet nozzle is joined to the nitrogen source gas supply nozzle at the junction, and wherein the halogen-based gas inlet nozzle supplies at least one halogen-based gas selected from a group consisting of a hydrogen halide gas and a halogen gas.