An image forming apparatus includes: a main body, a photosensitive body spreading developer on a printing paper, a developing roller supplying the photosensitive body with the developer, a developer regulating member regulating the amount of the developer supplied for the photosensitive body by the developing roller, the developer regulating member comprising a supporting member coupled to the main body and an elastic metal board having a bent part extended from the supporting member and contacting with the photosensitive body, and a free length of the elastic metal board being adjusted shorter as a draw rate of the elastic metal board material increases. Accordingly, a developing cartridge and an image forming apparatus has a free length of a developer regulating member that is adjustable to keep the density of developer uniform according to material characteristics of the developer regulating member.