A joint device includes a regulation device, a heating device, and a transparent portion. The regulation device includes a support base that includes a placement surface, and a regulation member. The heating device applies heat for causing solid phase diffusion at a joint interface between the two metal members by radiating an electromagnetic beam to a beam irradiated region via the regulation member. The beam irradiated region is set on a surface of one of the two metal members that is farther from the placement surface while the regulation device regulates motion of the two metal members. The transparent portion is provided at least at a portion corresponding to the beam irradiated region of the metal member to which the electromagnetic beam is irradiated, to transmit the electromagnetic beam.