To suppress falling off of an active material from a thin sheet-shaped current collector, enhancing the utilization factor of the active material, and improve cycle life characteristics.

A positive electrode unformed plate for a lead-acid battery comprising red lead oxide, monobasic lead sulfide, a binder of hydroxymethyl cellulose and that added with aluminum sulfate are used. As the method for adding the aluminum sulfate, active material paste for a positive electrode added with an aluminum sulfate aqueous solution is manufactured.