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 in a range of 0.5 mm from an end part of the corona bond 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 the cross-section of the boundary plating layer is 10% or more, 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.