A developing device includes a developing roller, a cover to cover the developing roller from above the developing roller, a filter to cover a vent of the cover to filter air and collect toner passing through the vent, and a pressing member engaged with the cover in which the filter is installed. The cover includes a projecting support to support the filter. The pressing member holds the filter between the pressing member and the cover. The projecting support is projected from one end toward the other end of the vent in a transverse direction of the vent at a part of the cover in a longitudinal direction of the developing roller to block the vent, and cantilevered on the one end. A gap is provided between a tip of the projecting support and an inner edge of the cover on the other end.