A windshield wiper arm , comprising: an arm piece which has a tip end, to which a wiper blade that wipes a wiping surface (S) is connected, and extends in a first direction (X); a hose to which a washer fluid is supplied and which is arranged along the arm piece ; and a washer nozzle which is connected to the hose and mounted on the arm piece on a base end side with respect to a portion connected to the wiper blade , wherein the washer nozzle comprises: a first flowpath which extends in the first direction (X); a second flowpath which is connected to the first flowpath and extends in a second direction (Z), which intersects the first direction (X) and in which the wiper blade is movable when wiping the wiping surface (S); a third flowpath which is connected to the second flowpath and extends in a third direction (Y), which intersects the first direction (X) and the second direction (Z) respectively and is along a normal line of the wiping surface (S); a fitting groove into which the arm piece is fitted and which extends along the first direction (X), the windshield wiper arm being characterized in that the fitting groove is open toward one side in the second direction (Z), a recess which is recessed in the third direction (Y) is formed on an inner surface of the fitting groove , and the recess is open in the first direction (X); and a protrusion which protrudes in the third direction (Y) and is fitted into the recess is formed on an outer surface of the arm piece . an arm piece which has a tip end, to which a wiper blade that wipes a wiping surface (S) is connected, and extends in a first direction (X); a hose to which a washer fluid is supplied and which is arranged along the arm piece ; and a washer nozzle which is connected to the hose and mounted on the arm piece on a base end side with respect to a portion connected to the wiper blade , wherein the washer nozzle comprises: a first flowpath which extends in the first direction (X); a second flowpath which is connected to the first flowpath and extends in a second direction (Z), which intersects the first direction (X) and in which the wiper blade is movable when wiping the wiping surface (S); a third flowpath which is connected to the second flowpath and extends in a third direction (Y), which intersects the first direction (X) and the second direction (Z) respectively and is along a normal line of the wiping surface (S); a fitting groove into which the arm piece is fitted and which extends along the first direction (X), the windshield wiper arm being characterized in that the fitting groove is open toward one side in the second direction (Z), a recess which is recessed in the third direction (Y) is formed on an inner surface of the fitting groove , and the recess is open in the first direction (X); and a protrusion which protrudes in the third direction (Y) and is fitted into the recess is formed on an outer surface of the arm piece . a first flowpath which extends in the first direction (X); a second flowpath which is connected to the first flowpath and extends in a second direction (Z), which intersects the first direction (X) and in which the wiper blade is movable when wiping the wiping surface (S); a third flowpath which is connected to the second flowpath and extends in a third direction (Y), which intersects the first direction (X) and the second direction (Z) respectively and is along a normal line of the wiping surface (S); a fitting groove into which the arm piece is fitted and which extends along the first direction (X), the windshield wiper arm being characterized in that the fitting groove is open toward one side in the second direction (Z), a recess which is recessed in the third direction (Y) is formed on an inner surface of the fitting groove , and the recess is open in the first direction (X); and a protrusion which protrudes in the third direction (Y) and is fitted into the recess is formed on an outer surface of the arm piece . <EOS>