The present invention relates to an air cleaner for killing the bacteria, viruses, mildew in the air with optoelectronic. A draft fan in the main body is used to suck the air. The air is then collected in an air collecting device after passing through an air collecting wall. An extreme ultraviolet ray transmitting tube is used to eliminate the bacteria, viruses, mildew in the air, and thereafter, the cleaned air is disposed by a negative ion cleaner. The fresh air is finally discharged through an air outlet.