Abstract: A device for reducing oocysts of Eimeria spp. uses microwave. In the device, when breeding broiler chickens, litter is recycled for second to fifth breeding after first breeding, and the hardened litter is crushed through a crushing device to form a floor similar to a first breeding environment and simultaneously microwaves of a microwave device are irradiated onto the crushed litter, so that various pathogenic organism such as oocysts of Eimeria spp., viruses, bacteria, parasites, and fungi in the litter are reduced or killed, and thus, pathogenicity and mortality become low, thereby healthily and safely breeding broiler chickens, and accordingly, providing great economic help to poultry farms.