Agents for surface treatment which can impart excellent corrosion resistance to zinc or zinc alloy products at low cost. The agents for the surface treatment of zinc or zinc alloy products of this invention include at least one water-soluble compound which contains antimony, bismuth, tellurium or tin. Ideally, a nickel salt and/or a manganese salt is also included, and most desirably tannins and/or thioureas are also included. Ideally, the zinc or zinc alloy products which have been immersed and treated in an aqueous solution which contains these agents for surface treatment are immersed in an aqueous solution which includes a sealing treatment agent selected according to the colour of the zinc or zinc alloy product to seal pinholes.