A metal member-welded structure includes: a Cu member; an Al member; and a welded portion formed by melting and solidifying each of materials of the Cu member and the Al member. The Cu member includes a Cu-based material containing Cu as a main component. The Al member includes an Al-based material containing Al as a main component and a plating layer that covers a side of the Al-based material, the side being close to a surface of the Cu member. The welded portion includes a sea-island structure in a vicinity of the surface of the Cu member. The sea-island structure includes: a plurality of island portions containing pure Al, and a sea portion interposed among the island portions. The sea portion has a eutectic structure having: a phase of an intermetallic compound of Cu and Al; and a phase of pure Al.