A buffer tank section (6) includes a liquid accumulation chamber (61) communicating with, through a liquid introduction flow path (42), a liquid tank (46) accumulation chemical liquid. A filter section (4) includes a filter inlet (41a) and a filter outlet (41b), wherein the filter inlet (41a) communicates with a liquid discharge vent (60d) of the buffer tank section (6). In a pump (11), a pump inlet (11a) is connected to the filter outlet (41b) and a pump outlet (11b) is connected to a discharge nozzle (50) through a liquid discharge flow path (47). A return flow path (48) is connected between the pump outlet (11b) and the buffer tank section (6), wherein the chemical liquid, discharged from the pump (11), is returned to the liquid accumulation chamber (61). An exhaust flow path (49) is connected to the buffer tank section (6), thereby exhausting air in the liquid accumulation chamber (61).