To provide a coating agent composition for rustproofing excellent in rustproof properties, enabling thin coating, and having alkali resistance, water resistance, solvent resistance, processability and excellent adhesiveness to a metal material, and a laminated metal material.

The coating agent composition for rustproofing is characterized in that it is an aqueous emulsion containing a below-mentioned polyolefin resin, the number average particle size of the polyolefin resin is ≤1 μm, and the aqueous emulsion is substantially free from an emulsifier component or a compound having a protective colloid effect. The polyolefin resin is as follows: a copolymer constituted of (A1) an unsaturated carboxylic acid or its anhydride, (A2) an ethylenic hydrocarbon and (A3) at least one kind of compound expressed by any one of formulas (I) to (IV); and the weight ratios of each constituting component (A1) to (A3) satisfy relationship (1): 0.01≤(A1)/{(A1)+(A2)+(A3)}×100<5 and relationship (2): (A2)/(A3)=55/45 to 99/1.