A developing device includes a developing roller, a developing case, and a support. The developing roller includes a sleeve and a magnetic field generator. The sleeve is rotatable and includes a hollow shaft at an axial end of the sleeve. The magnetic field generator is irrotationally disposed inside the sleeve and includes a non-rotating shaft at an axial end of the magnetic field generator. The non-rotating shaft penetrates through the hollow shaft and projects outward. The developing case is configured to store developer and rotatably supports the hollow shaft. The support includes a fitting portion into which the non-rotating shaft of the magnetic field generator is irrotationally fitted. The support is supported on the developing case using the fitting portion as a main-positioning portion.