A manufacturing method for a joint part in which a first metal piece and a second metal piece are joined to each other by performing welding by irradiating a high-energy beam to a joint surface on which the first metal piece and the second metal piece face each other, the first metal piece including a first flow path for passage of a fluid provided at a specific depth from a surface on a side exposed to the high-energy beam, the second metal piece including a second flow path for passage of the fluid provided at a specific depth from the surface on the side exposed to the high-energy beam, and the first flow path and the second flow path being coupled to each other on the joint surface.