PURPOSE: To separate and remove only mixed toner and form a clear image having no color mixture all the time by arranging a separation roller which has a minus and a plus inversion layer formed alternately in developing devices of the 2nd and succeeding colors.

CONSTITUTION: The mixed toner separation roller 43 which has a minus inversion layer 52 and a plus inversion layer 51 formed alternately having a frictional electrostatic charging sequence as shown in a figure is arranged in the 2nd developing device 41 of the dichroic recording device. If red toner 33 from a precedent stage enters the 2nd developing device 41, the red toner 33 is inverted in polarity to plus, zero, minus, zero, and plus repeatedly by the separation roller 43 because of a difference in frictonal electrostatic charging sequence, so that the amount of charges are decreased. Consequently, only the red toner 33 is separated and removed by the roller 33 without combining with black toner 34, and then stored in a lower reservoir part 44. Therefore, clear images having no color mixture are formed all the time.