Abstract: An air cleaner having a minus ion generator and a positive electrode. The minus ion generator carries a high minus voltage, and the positive electrode carries a high plus voltage. Preferably, the minus ion generator has a heater. The air cleaner may have an absorbing sheet positioned close to the positive electrode. Preferably, the minus ion generator is spaced apart from the positive electrode by a distance not less than a half of the maximum distance between walls of room. Preferably, the high plus voltage is not less than 4,000 Volts, and the absolute value of the high minus voltage is larger than the absolute value of the high plus voltage. Preferably, the air cleaner has a sterilizing function.