PROVIDED IS AN ANTIBACTERIAL AGENT USEFUL FOR REMOVAL OF PINK STAINS OR PINK BIOFILMS PRODUCED IN THE LIVING ENVIRONMENT. THE INVENTION RELATES TO AN ANTIBACTERIAL AGENT INCLUDING A COMBINATION OF A QUATERNARY AMMONIUM SALT REPRESENTED BY THE FOLLOWING COMPONENT (A) AND AN ORGANIC SOLVENT REPRESENTED BY THE FOLLOWING COMPONENT (B): (A) ONE OR MORE QUATERNARY AMMONIUM SALTS SELECTED FROM THE GROUP CONSISTING OF A DIALKYLDIMETHYLAMMONIUM SALT AND AN ALKYLBENZYLDIMETHYLAMMONIUM SALT AND (B) ONE OR MORE ORGANIC SOLVENTS SELECTED FROM THE GROUP CONSISTING OF AN AROMATIC ALCOHOL, AN AROMATIC ALDEHYDE, AND COMPOUNDS REPRESENTED BY THE FOLLOWING FORMULAE (1) AND (2) WHEREIN R REPRESENTS AN ALKYL GROUP OR AN ALKENYL GROUP HAVING 5 TO 10 CARBON ATOMS, OR A BENZYL GROUP, A REPRESENTS AN ALKYLENE GROUP HAVING 1 TO 10 CARBON ATOMS, AND N DENOTES A NUMBER FROM 0 TO 5 WHEREIN NAS MAY BE THE SAME OR DIFFERENT FROM EACH OTHER.
