A developing device is capable of preventing developing agent from leaking from a developing frame of a developer cartridge. The developer cartridge includes a developing agent carrying member including a rubber roller, a first seal including a first fluffing member, and a second seal including a second base member and a second fluffing member fixed thereto. The second base member and the second fluffing member have downstream end portions in a rotational direction of the developing agent carrying member. The downstream end portion of the second base member is positioned upstream of the downstream end portion of the second fluffing member. The downstream end portion of the second fluffing member is nipped between the first fluffing member and the rubber roller.