To provide a cold-rolled coated steel panel enhanced in the corrosion resistance of an undercoating film to a steel panel, low in cost and excellent in processability.

An undercoating film layer containing a corrosion inhibitor (A) which is obtained by bonding corrosion suppressing calcium ions to porous silica particles by ion exchange, and a polyphosphate (B) is formed on the surface of a cold-rolled steel panel to which chemical forming treatment is applied. The undercoating film layer comprises a composition prepared by adding 2-50 pts. mass of the corrosion inhibitor (A), which is obtained by bonding corrosion suppressing calcium ions to porous silica particles by ion exchange, to 100 pts. mass of the resin component of the undercoating film layer, and adding the polyphosphate (B) to the resin component so that a ratio of the corrosion inhibitor (A) and the polyphosphate (B) is set to A/B=60/40-5/95 as a mass ratio. The addition amount of both of the corrosion inhibitor (A) and the polyphosphate (B) becomes 5-150 pts. mass with respect to 100 pts. mass of the resin component. By this constitution, the coated cold-rolled steel panel is further excellent in corrosion resistance.