A piston cooling system includes: a nozzle pipe portion which communicates with an oil passage which is provided in an internal combustion engine and which extends towards an interior of a cylinder bore; and a flow path forming member which is fixed to a distal end portion of the nozzle pipe portion and in which a plurality of oil jetting paths are formed, wherein: the distal end portion comprises an expanded pipe portion where the nozzle pipe portion is expanded and the flow path forming member is fittingly inserted into the expanded pipe portion; the flow path forming member has a distal end face which is exposed to an exterior portion at a distal end side of the expanded pipe portion; and the flow path forming member is locked in the expanded pipe portion by deforming a distal end edge of the expanded pipe portion.