Disclosed is a coating liquid characterized by comprising a hydroxyl group-containing resin, an organic acid and/or a derivative thereof contained in a polar solvent, the hydroxyl group-containing resin being at least one resin selected from (1) polyvinyl acetal resins, (2) ethylene-vinyl alcohol copolymers, (3) unmodified and/or modified polyvinyl alcohols, and (4) cyanoethyl group-containing polymers. Also disclosed are a coating liquid for manufacturing an electrode plate, an undercoating agent, and use thereof. The coating liquid capable of forming a film, which has excellent adhesion and solvent resistance, on the surface of a metal material such as an aluminum material can be provided. Furthermore, a coating liquid for manufacturing an electrode plate for a battery or a polarizing electrode plate for a capacitor comprising an active material layer having excellent adhesion and electrolyte resistance to a current collector formed of, for example, an aluminum foil or a copper foil and having an improved contact resistance to the current collector, an undercoating agent, an electrode plate; a method for manufacturing the electrode plate, a battery, and a capacitor can be provided.