A developing device is provided with a case main body, a developing roller coupled with the case main body, an axis direction seal member coupled with the case main body, and a side seal member coupled with the case main body. The axis direction seal member and the side seal member make contact with one another such that there is no gap between the axis direction seal member and the side seal member in a rotation axis direction of the developing roller. In a rotation direction of the developing roller, an upstream end of the side seal member is located downstream of an upstream end of a contact area between the axis direction seal member and the developing roller.