Abstract: An automatic air cleaner has a case and a base; wherein the case has a central cavity provided with a number of receiving grooves defined by ribs disposed at both inner lateral walls of the central cavity for a dust collecting plate and a filter plate to be inserted therein. Dirty air pumped into the case body is cleaned in sequence, moving from the dust collecting plate having rectangular dust collecting members cooperating with electric discharge rods, the filter plate made up of non-woven fabric and provided with an odoriferous agent, and then an ozone tube whose generation of ozone contributes to the termination of bacteria existing in the air. Finally anion pins are adapted to electrify the dust left over in the air so that when the fresh air blown out of the through slots of the case by fans driven by motors, the dust will drop onto the ground. In addition, the dust collecting plate, filter plate, and ozone tube can be easily replaced or withdrawn for cleaning in maintenance.