An image forming apparatus and a developer thereof includes a developer frame to store a developing agent, a developing device rotatably mounted to the developer frame, a support member mounted to the developer frame, and a regulating member having a first end fixed to the support member, and a second end opposite to the first end, the second end installed in a trail-type manner. The support member includes a plurality of bending portions bent to reinforce a strength of the support member. A trail-type regulating device improved to maintain a sufficient strength and a sufficient elasticity is also disclosed. The regulating device allows the developing agent layer attached to the developing device can be uniform.