A developing device capable of improving the fluidity of a developer and alleviating the stress generated in the developer, and a process cartridge and an image forming apparatus that use this developing device. In a connecting portion, there is formed a storage portion for storing the developer, in which the cross-sectional area thereof has width D2 that continuously becomes wider toward the top, compared to the width D1 of the cross-sectional area of an opening portion by which the developer is lifted up from the second screw, and becomes wider than D1 at the central part thereof. Furthermore, the width of the cross-sectional area thereof continuously becomes narrow.