There is provided a developing device including: a casing; a developing roller held by the casing and carrying a developing agent; and a layer-thickness regulating blade for regulating a layer thickness of the developing agent carried on the developing roller, in which in the state where the developing roller is held by the casing, the tip end portion of the layer-thickness regulating blade abuts against the developing roller at a uniform pressure in the axial direction of the developing roller, and in the state where the developing roller is not held by the casing, the layer-thickness regulating blade is bent toward a disposed position of the developing roller.