PURPOSE: To obtain an air cleaner with improved collection efficiency by a design in which a sheet-like filter is spread in a zigzag folded-back manner and ultrasound vibrators are provided in the recessed parts between the folded filter planes and a filter washing water atomization mechanism is provided.
CONSTITUTION: An air cleaner consists of filter units 1 which is formed by folding back a sheet-like filter in zigzag manner, vertically provided in a three- tier casing. Below each filter unit 1, a washing water receiving tray 2 is mounted, so that washing water can be sprayed to an air intake face 5 from spray nozzles 3. In addition, in the recessed part, created by the zigzag folding- back of each filter unit 1, of the filter an ultrasound vibrator is mounted. Consequently, moisture in the filter moistened by the washing water can be easily evaporated by generation of an ultrasound.