PURPOSE: To prevent the leakage and scattering of the toner with a simple constitution, by winding a covering member at the outer circumference of a rotary developing device which contains the developing units of different colors in plural section and covering the developing ports which are not used.

CONSTITUTION: For a rotary developing device 14, the inside of a main body case 140 is divided into plural sections. Then the developing units 19W22 containing the yellow, magenta, cyan and black developers are set in those divided sections respectively. The magnet rollers 19aW22a are provided along with the cleaning blades 19bW22b, and the developing ports 14aW14d are formed to the case 140 at each position corresponding to each magnet roller. A covering member 15 is made of a long paper sheet, etc. and wound round a draw-out roller 24. The member 15 is wound to the device 14 so as to cover the ports 14bW14d which are not used by the guide rollers 25W27. Then the tip part of the member 15 is wound round a roller 28.