PROBLEM TO BE SOLVED: To miniaturize a discharge unit, and to allow processed air to flow smoothly through a ventilation passage of the discharge unit.SOLUTION: A discharge unit (23) includes a casing (30) for storing a discharge electrode (50), a counter electrode (54) and a voltage impression part (43). The casing (30) forms a ventilation passage (70) in which the discharge electrode (50) and the counter electrode (54) are installed, and through which processed air is allowed to flow. Further, the voltage impression part (43) is arranged on the side of the ventilation passage (70) in the casing (30).