A surface treated steel sheet has a surface treatment film including a metallic compound containing titanium, a metallic compound containing magnesium, a cationic urethane resin having at least one cationic functional group selected from primary to tertiary amino groups and quaternary ammonium bases, and a cationic phenol polycondensate which is a polycondensate of a phenol compound with an aldehyde and has a cationic functional group, wherein the titanium content in the surface treatment film is in the range of 1 mass % to 4 mass % based on a total solid content; the magnesium content in the surface treatment film is in the range of 0.2 mass % to 2 mass % based on a total solid content; the cationic urethane resin content in the surface treatment film is in the range of 20 mass % to 35 mass % based on a total solid content; the cationic phenol polycondensate content in the surface treatment film is in the range of 25 mass % to 40 mass % based on a total solid content; and the mass ratio of the cationic urethane resin to the cationic phenol polycondensate is in the range of 33.3:66.7 to 49:51.