Surface-treated steel sheet

A surface-treated steel sheet comprising:

• a Zn—Al—Mg-containing plating layer located on a surface of a steel sheet serving as a base material;
• a primer coating layer located on the Zn—Al—Mg-containing plating layer, and containing at least a vanadium compound;
• and
• an upper coating layer located on the primer coating layer, wherein:
• an intensity of vanadium at an interface on the upper coating layer side of the primer coating layer, which is calculated based on a depth profile regarding a distribution of a vanadium element obtained by analyzing the primer coating layer according to a glow discharge spectrometry, is 50% or less relative to a maximum intensity of vanadium in the primer coating layer, which is calculated based on the depth profile;
• and
• an average intensity of vanadium is 0.8% or more relative to an average intensity of magnesium, 1.8% or more relative to an average intensity of aluminum, and 0.6% or more relative to an average intensity of zinc in a range to 1 μm toward the upper coating layer side in a thickness direction from an interface on the Zn—Al—Mg-containing plating layer side of the primer coating layer, which is calculated based on the depth profile.