A device for developing an electrostatic latent image that includes a developing roller which is disposed in a developing housing, holds the developing agent on its peripheral surface, and conveys the developing agent that is held to a developing zone, a feeding roller for feeding the developing agent onto the peripheral surface of the developing roller, and seals that are disposed so as to be opposed to both ends of the developing roller from the downstream side of the developing zone to the upstream side of a developing agent-limiting zone. The device further includes seal lips that are formed in a protruding manner and which extend from one end on the side of the developing zone to an opposite end on the side of the developing agent-limiting zone. The feeding or replenishing roller is positioned so that its end surfaces are in contact with the inner end surfaces of the seals.