In addition to the above-described typical examples of the developers, the developer containing an oxyacid (e.g., lactic acid) or a keto-acid (e.g., levulinic acid) described in Japanese Patent Application (OPI) No. 138901/75, the developer containing lactam described in Japanese Patent Application (OPI) No. 59504/76, the developer comprising an alkaline aqueous solution containing 2 to 50% by wei