A developing device includes a housing, a developing roller, a developer supply path, a developer conveyance path, a supply-side conveying member, an agitating side conveying member and first projection members. The developing roller is rotatably supported in the housing. The supply-side conveying member includes a supply-side spiral member formed by connecting spiral pieces, in the first direction and having a hollow interior formed by the connected spiral pieces and a first rib member extending in the first direction, is arranged in the developer supply path and conveys the developer in the first direction by being driven and rotated. The first projecting members extend in the first direction along an outer wall portion of the first rib member from a first area where the supply-side spiral member and the first rib member intersect and project radially outward in the rotation of the supply-side conveying member.