The present invention provides a developing device, toner cartridge, process cartridge, and image forming apparatus. The electrophotographic photoreceptor comprises a layered-type photosensitive layer in which a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are stacked, formed on a conductive supporting member made of a conductive material, wherein the electrophotographic photoreceptor has high sensitive characteristics to a semiconductor laser beam having a wavelength ranging from 380 to 500 nm; the charge transporting layer of the layered-type photosensitive layer contains as the charge transporting material, a triarylamine dimer compound represented by the general formula (1): and a film thickness of the photosensitive layer is less than 30 mum or.