A developing device includes a developer container configured to accommodate a developer containing toner and a carrier, and a feeding screw provided rotatably in the developer container and configured to feed the developer in a predetermined feeding direction. The feeding screw includes a rotation shaft, and a first helical blade and a second helical blade which are formed around the rotation shaft and which form a multi-thread helical blade. The feeding screw includes a region in which a plate-like projection portion is provided on the rotation shaft between the first helical blade and the second helical blade. The plate-like projection portion is provided to contact an adjacent helical blade on a downstream side with respect to the feeding direction without contacting an adjacent helical blade on an upstream side with respect to the feeding direction.