A welding assistance member with electrically-conductive properties is used for spot-welding performed by sandwiching a second member between electrically-conductive first members different in material from the second member. The welding assistance member is fitted into a hole extending through the second member so as to allow for spot-welding of the first members to each other from opposite sides in the hole. The welding assistance member includes: a main body that has a size and shape that allow a gap to be formed between the main body and an inner side surface of the hole when the main body is fitted in the hole; and a position maintaining component that is provided at an outer side of the main body, has heat, heat resisting, and electrically insulating properties, and maintains the main body in a separated state from the inner side surface. A spot-welding method uses this welding assistance member.