A welding structure of metal members includes a first member having a first opposing surface, a second member having a second opposing surface, and a welding portion fixing the first member and the second member to each other. A gap is formed between the first opposing surface and the second opposing surface. R1>R2 is satisfied where R1 represents a width of the welding portion in the gap and R2 represents a width of the welding portion on the first opposing surface of the first member. T2>T1 is satisfied where T2 represents a thickness of the second member in the portion where the welding portion is formed and T1 represents a thickness of the first member in the portion where the welding portion is formed. 0.8≤D1/T1≤1.2 is satisfied where D1 represents a depth of the welding portion in the second member from the second opposing surface.