To provide a coating film formation method for obtaining a coating film maintaining water sealing ability and exhibiting a substrate protection effect for a long duration and excellent in stain-proofness.

This coating film formation method involves (1) forming an undercoat by using an undercoating material containing (a) a synthetic resin emulsion, (b) a water-dispersion type water-repelling agent at a ratio of 1-100 pts.wt. to 100 pts.wt. of the component (a), and (c) a pigment at a concentration of 30-90% by pigment volume and after that (2) applying a topcoating material containing a compound and/or a polymer having reactive silyl group.