A device and a method for decontaminating the interior of a biosafety cabinet using a drug considered to be safe for humans, particularly peracetic acid, are provided. The device comprises an ultrasonic atomizer (1) for atomizing a peracetic acid disinfectant using ultrasound and releasing droplets； a diffusion fan (2)； a circulation fan (4)； a temperature-humidity sensor (3)； and a controller (5).
