The object of the present invention is to provide a metal surface treatment agent which improves the press molding workability of metal materials, and which can form a coating film that is superior in terms of at least one of moisture resistance and coating film stripping characteristics. The metal surface treatment agent of the present invention comprises (A) a copolymer which comprises (a) styrene and (b) a vinyl compound with carboxyl groups that is copolymerizable with styrene, and (B) a lubricating agent. The metal surface treatment agent is characterized by the fact that the weight ratio of component (a) to component (b) in the aforementioned polymer (A), i.e., (a)/(b) (weight ratio), is in the range of 1/9 to 9/1, the proportion of (a)null(b) in the aforementioned polymer (A) is 30 to 100 weight %, and the weight ratio of (B) to (A)null(B) is 2 to 30 weight %.