Welded joint and automobile member

A welded joint comprising a first steel sheet, a second steel sheet, and a spot welded part joining the first steel sheet and the second steel sheet, wherein,

• a first plating layer is provided on a surface of the first steel sheet facing the second steel sheet,
• no plating layer is present on or a second plating layer is provided on a surface of the second steel sheet facing the first steel sheet,
• the spot welded part has a nugget and corona bond,
• a boundary plating layer is provided between the first steel sheet and the second steel sheet from an end part of the corona bond to 0.5 mm from the end part of the corona bond in a direction toward an outside of the spot welded part,
• a higher tensile strength of a tensile strength of the first steel sheet and a tensile strength of the second steel sheet is 780 MPa or more,
• an area ratio of a MgZn2 phase at a cross-section of the boundary plating layer is 10% or more, the cross-section of the boundary plating layer being a cross-section of the welded joint running through a center of the nugget and along a thickness direction of the first steel sheet, and
• the first plating layer and the second plating layer satisfy the following Relation I:
• 0.30≥[(Mg composition of the first plating layer(mass %))×(amount of deposition of the first plating layer(g/m2))+(Mg composition of the second plating layer(mass %))×(amount of deposition of the second plating layer(g/m2))]/[(Zn composition of the first plating layer(mass %))×(amount of deposition of the first plating layer(g/m2))+(Zn composition of the second plating layer(mass %))×(amount of deposition of the second plating layer(g/m2))]≥0.06 Relation I
• where, if no second plating layer is present, the Mg composition, Zn composition, and amount of deposition of the second plating layer are 0.