A developing device includes: a frame having an opening; a developer carrying member rotatably supported to the frame; and a side seal. The developer carrying member is rotatable about its axis in a rotating direction and has an axial end portion in an axial direction. The side seal is disposed between the frame and a peripheral surface of the axial end portion, and has a contact member contacting the peripheral surface. The contact member includes: a first seal member disposed adjacent to an edge of the opening in the axial direction; and a second seal member disposed adjacent to and upstream of the first seal member in the rotating direction. The first seal member permits developer to move inward in the axial direction and provides a mobility of developer therein higher than that of the second seal member that is made of a material that restricts movement of developer.