Disclosed are apparatus and method for decontaminating and sterilizing chemical and biological agents, which can efficiently decontaminate and sterilize high precision electronic devices, communication devices, computers or inside of vehicles and air planes contaminated with chemical and biological agent by using mixture of non-thermal atmospheric pressure air plasma and oxidizing peroxide vapor. The apparatus according to the present invention comprises a decontamination and sterilization chamber 10; a first fluid supplying line L1 and a second fluid supplying line L2, which are installed in the form of closed circuit between the inlet 11 and outlet 12 of the decontamination and sterilization chamber 10; a peroxide vapor supplier which is installed on the first fluid supplying line; and a non-thermal atmospheric pressure air plasma reactor 70 which is installed on the second fluid supplying line L2.