To provide a joined structural material with which gas bubble in the inner part of a soldered member after joining is reduced.

Materials set along the peripheral edge part in a joining range forming the soldering member 13 formed as a frame-state between the joining surface of a first joining member 11 and the joining surface of a second joining member 12, are held into a vessel filled up with inert gas or mixed gas of the inert gas and hydrogen gas, and the soldering member is melted by rising the atmospheric temperature in the vessel to not lower than the liquidus of the soldering member, and while holding the atmospheric temperature in the vessel to not lower than the liquidus of the soldering member, the pressure in the vessel is reduced to a first pressure. While holding the atmospheric temperature in the vessel to not lower than the liquidus of the soldering member, the inert gas is supplied into the vessel and the pressure in this vessel is pressurized to a second pressure, and the soldering member is solidified by lowering the atmospheric temperature in the vessel to not higher than the solidus of the soldering member, and thus, the joined structural material 1 provided with the first joined member, the second joined member and the soldered member for joining the first joining member and the second joining member is manufactured.