Patent ID: 8369737

Claim:
A developing device, comprising: a casing that has: a housing part that houses a developer; an upstream edge and a downstream edge positioned in an upstream side and a downstream side of a rotation direction of a developer conveying body, respectively; and a rectangular opening that opposes a development region for performing development with the developer, the rectangular opening being provided between the upstream edge and the downstream edge; a cylindrical developer conveying body that is provided inside of the casing to rotate in a state of passing the rectangular opening, the cylindrical developer conveying body conveying the developer to the development region by holding the developer on an outer circumferential surface; a flexible sheet member that has an upstream end part and a downstream end part positioned in an upstream side and a downstream side of the rotation direction of the developer conveying body, respectively, the upstream end part of the flexible sheet member being fixed at the downstream edge of the casing, the downstream end part of the flexible sheet member being a free end and coming into contact with a layer of the developer in a rotation axis direction of the developer conveying body at a position of the developer conveying body which passes the downstream edge of the opening, the layer of the developer being held on the outer circumferential surface portion of the developer conveying body working out to a developer holding region, and developer leakage-preventing members that are provided inside of the casing in a state of coming into contact respectively with both end parts of the outer circumferential surface positioned on outer sides of the developer holding region in the rotation axis direction of the developer conveying body at a position of the developer conveying body which passes the downstream edge of the opening, and both end parts of the sheet member in the rotation axis direction of the developer conveying body each extend to a position overlapping with a part of the developer leakage-preventing member, wherein the sheet member has notch parts at the both end parts, overlapping with the developer leakage-preventing members, positioned between the upstream end part and the downstream end part of the sheet member, for avoiding contact with upstream corner parts of the developer leakage-preventing members by enclosing the upstream corner parts with the notch parts.