A layer thickness restricting blade may include an arm main body and a contact portion provided at a front end portion of the arm main body. The contact portion may be configured by inserting a rubber member made of polyurethane to a rubber member made of silicone. The contact portion may be brought into contact with a surface of a developing roller and be gradually worn in accordance with rotation of the developing roller. When a revolution number of the developing roller reaches a rectified revolution number, a polyurethane layer at inside thereof may be exposed to a surface. Thereby, a failure in charging may be brought about in a toner at the portion, further, a failure in an image may be brought about on a sheet and therefore, by bringing about the failure in the image, an operator may be informed that a timing of interchanging the toner is reached.