PURPOSE: To enhance indoor purification effect by ejecting clean pressure air from an ejection hole on the side wall of an air shower room and sucking in indoor air from suction holes on a floor surface and a side wall surface and making controllable the suction air rate of the holes between the floor surface and the side wall surface.

CONSTITUTION: A pressure air is boosted into a clean air supply chamber 14 by driving an air supply fan 15 so as to eject the pressure air into an air shower room 4 from an ejection nozzle 12 by way of a filter 13. The air in the air shower room 4 is sucked in from each of suction holes 24 and 31 bored on a side wall 11 and a floor surface 30 and fed in the suction chamber 22 by way of prefilters 25 and 33, then the air is supplied to a clean air supply chamber 14 by driving the air supply fan 15 so as to circulate. In this case, a suction air quantity from the suction hole 31 on the floor surface 30 is adapted to exceed a suction an air quantity from the suction hole 24 on the side wall 11 while the ratio between the both suction quantities is controlled by a control means 40, such as an air quantity control damper. This construction makes it possible to eliminate effectively both dust and dirt floating in the air shower room 4 and dust and dirt falling to the floor surface by sucking in the dust and dirt.