A welding torch comprising: a first wire passage having a first wire inlet port and a first wire outlet port, the first wire inlet port allowing a first welding wire to enter thereto, the first wire outlet port allowing the first welding wire to be output therefrom; a second wire passage having a second wire inlet port and a second wire outlet port, the second wire inlet port allowing a second welding wire to enter thereto, the second wire outlet port allowing the second welding wire to be output therefrom; a third wire passage having a third wire inlet port and a third wire outlet port, the third wire inlet port allowing a portion of the first welding wire output from the first wire outlet port and a portion of the second welding wire output from the second wire outlet port to enter thereto, the third wire outlet port allowing the portion of the first welding wire and the portion of the second welding wire to be output therefrom; a wire detection space connected to the first wire outlet port, the second wire outlet port, and the third wire inlet port, the wire detection space allowing the portion of the first welding wire and the portion of the second welding wire to pass through the wire detection space; characterized in that the welding torch further comprises a gas inlet provided at the wire detection space to supply a shielding gas to the wire detection space; a wire detecting device configured to detect the portion of the first welding wire and the portion of the second welding wire in the wire detection space, wherein the wire detecting device includes an irradiator that emits detection light, and a photodetector that receives the detection light, and the wire detecting device is arranged to detect the presence of the first welding wire and the second welding wire in front of the position where the welding wires merge together. a first wire passage having a first wire inlet port and a first wire outlet port, the first wire inlet port allowing a first welding wire to enter thereto, the first wire outlet port allowing the first welding wire to be output therefrom; a second wire passage having a second wire inlet port and a second wire outlet port, the second wire inlet port allowing a second welding wire to enter thereto, the second wire outlet port allowing the second welding wire to be output therefrom; a third wire passage having a third wire inlet port and a third wire outlet port, the third wire inlet port allowing a portion of the first welding wire output from the first wire outlet port and a portion of the second welding wire output from the second wire outlet port to enter thereto, the third wire outlet port allowing the portion of the first welding wire and the portion of the second welding wire to be output therefrom; a wire detection space connected to the first wire outlet port, the second wire outlet port, and the third wire inlet port, the wire detection space allowing the portion of the first welding wire and the portion of the second welding wire to pass through the wire detection space; characterized in that the welding torch further comprises a gas inlet provided at the wire detection space to supply a shielding gas to the wire detection space; a wire detecting device configured to detect the portion of the first welding wire and the portion of the second welding wire in the wire detection space, wherein the wire detecting device includes an irradiator that emits detection light, and a photodetector that receives the detection light, and the wire detecting device is arranged to detect the presence of the first welding wire and the second welding wire in front of the position where the welding wires merge together.