A method for manufacturing a welded structure including two or three steel sheets (11, 12) and a lapped portion in which the steel sheets are overlapped and joined by spot welding at a plurality of locations, the method comprising: carrying out spot welding, the carrying out spot welding including a first step in which a first rod-shaped electrode body and a second rod-shaped electrode body are arranged facing each other with the lapped portion being sandwiched therebetween, and a first ring-shaped member and a second ring-shaped member are arranged facing each other, the first ring-shaped member having a through hole through which the first electrode body is inserted and a back end to which a first elastic body is connected and the second ring-shaped member having a through hole through which the second electrode body is inserted and a back end to which a second elastic body is connected, and a second step in which the lapped portion is pressurized by pressing a tip face (21aa, 31aa) of each of the first electrode body and the second electrode body against the lapped portion, and by pressing a tip face (22a, 32a) of each of the first ring-shaped member and the second ring-shaped member against the lapped portion while the first elastic body exerts a pressing pressure on the first ring-shaped member and the second elastic body exerts a pressing pressure on the second ring-shaped member, and then an electric current is applied between the first electrode body and the second electrode body, wherein the first step and the second step cause a spot weld portion to satisfy a condition (a) or a condition (b) below in accordance with an average thickness t ave (mm): (a) d ng > d(t ave)1/2 when 0.5 mm ≤ t ave < 1.1 mm (b) d ng > 1.05d when 1.1 mm ≤ t ave ≤ 2.6 mm where d ng (mm) is a nugget diameter, d (mm) is a tip diameter of an electrode used by the spot welding, and t ave (mm) is an average thickness per steel sheet of the steel sheets at the lapped portion. carrying out spot welding, the carrying out spot welding including a first step in which a first rod-shaped electrode body and a second rod-shaped electrode body are arranged facing each other with the lapped portion being sandwiched therebetween, and a first ring-shaped member and a second ring-shaped member are arranged facing each other, the first ring-shaped member having a through hole through which the first electrode body is inserted and a back end to which a first elastic body is connected and the second ring-shaped member having a through hole through which the second electrode body is inserted and a back end to which a second elastic body is connected, and a second step in which the lapped portion is pressurized by pressing a tip face (21aa, 31aa) of each of the first electrode body and the second electrode body against the lapped portion, and by pressing a tip face (22a, 32a) of each of the first ring-shaped member and the second ring-shaped member against the lapped portion while the first elastic body exerts a pressing pressure on the first ring-shaped member and the second elastic body exerts a pressing pressure on the second ring-shaped member, and then an electric current is applied between the first electrode body and the second electrode body, a first step in which a first rod-shaped electrode body and a second rod-shaped electrode body are arranged facing each other with the lapped portion being sandwiched therebetween, and a first ring-shaped member and a second ring-shaped member are arranged facing each other, the first ring-shaped member having a through hole through which the first electrode body is inserted and a back end to which a first elastic body is connected and the second ring-shaped member having a through hole through which the second electrode body is inserted and a back end to which a second elastic body is connected, and a second step in which the lapped portion is pressurized by pressing a tip face (21aa, 31aa) of each of the first electrode body and the second electrode body against the lapped portion, and by pressing a tip face (22a, 32a) of each of the first ring-shaped member and the second ring-shaped member against the lapped portion while the first elastic body exerts a pressing pressure on the first ring-shaped member and the second elastic body exerts a pressing pressure on the second ring-shaped member, and then an electric current is applied between the first electrode body and the second electrode body, wherein the first step and the second step cause a spot weld portion to satisfy a condition (a) or a condition (b) below in accordance with an average thickness t ave (mm): (a) d ng > d(t ave)1/2 when 0.5 mm ≤ t ave < 1.1 mm (b) d ng > 1.05d when 1.1 mm ≤ t ave ≤ 2.6 mm (a) d ng > d(t ave)1/2 when 0.5 mm ≤ t ave < 1.1 mm (b) d ng > 1.05d when 1.1 mm ≤ t ave ≤ 2.6 mm where d ng (mm) is a nugget diameter, d (mm) is a tip diameter of an electrode used by the spot welding, and t ave (mm) is an average thickness per steel sheet of the steel sheets at the lapped portion.