PURPOSE: To raise the density of an ink mist by providing an opening window opposed to the moving path of a recording medium, on a part of a side wall, making an ink mist obtained by excitation circulate in a duct whose both ends are communicating with the space part of an ink tank, making it adhere to the recording medium from the opening window to execute a development.

CONSTITUTION: Ink 2 is excited by operating an exciting device 3 to produce an ink mist in a space part in the ink tenk 1. When a pump 7 is operated simultaneously, the ink mist is attracted from one end part of a duct 11, its one part is attracted selectively to a recording paper 10 by an opening part 8, to execute the development and the ink mist does not contributed to the development circulates in the duct 11 and returns to the ink tank 1. Both ends of the duct 11 communicate with each other, and the ink mist returned to the ink tank 1 from the other end is attracted from one end of the duct 11 and circulates together with an ink mist generated new. Therefore, the density of the ink mist in the duct 11 can be raised, the utilizing efficiency of the ink mist is raised, to execute the development having a good contrast and to obtain the satisfactory responsiveness in case of varying the density.