PURPOSE: To record a stable, high-quality image by dividing the inside of a storing vessel into two sections by a carrier holding member possessing plural openings larger than the grain size of a magnetic developer and smaller than the grain size of a magnetic carrier and keeping the volume of carriers on a developer carrying roll constant.

CONSTITUTION: A mesh 10 is provided as a carrier holding member, opposite to a part of the developer carrying roll 1 facing the storing vessel 2, and divides the storing vessel into two spaces 11a and 11b. The size of the mesh 10 is smaller than the grain size of the carrier 4 and larger than the grain size of toner 3. Consequently, the carriers 4 flow only in the space 11a facing the developer carrying roll 1, and never moves to the space 11b. The toner 3 in the space 11b can move through the mesh 10 and shifts to the space 11a. Thus, the concentration of the toner in the space 11a, that is, on the sleeve 1a, can be kept constant, whereby the variance of image density can be prevented.