A water-based lubricant for plastic working of a metallic material is obtained by adding to a water-based medium: (A) a polymer and/or a salt thereof containing a carboxylic acid or a derivative thereof as a constituent monomer; (B) an oxoacid of tungsten, of silicon, or of phosphorus, or a condensate thereof, and/or a salt thereof; (C) a hydroxide of an alkali metal; and (D) a lubricating component (D), and the solid content weight ratio (A)/[(A)+(B)+(C)+(D)] is 0.05 to 0.4.