Bakanae disease, a typical seed-borne disease of rice, caused by Gibberella fujikuroi which affected rice quality and yields seriously throughout the country. The disease could be transmitted to other healthy plants in heading dates, and the environment-friendly agricultural practices could be one of the reasons for the outbreak of disease because of the chemical-free agriculture. Studies were conducted to investigate the effects of instrument devised to protect the bakanae disease. The newly developed device consists of aquarium heater and oxygen generator. The temperature of water remained stable as 32.6±0.9℃, and it was effectively applied to sterile seeds for high quality seedlings. In the field tests of infected seeds with bakanae disease, the ripened grain ratio decreased in the 30% infected seeds, and the yields of polished rice dropped as 28%. The secondary infection of bakanae disease was effectively prevented with 500 fold fludioxonil treatments just prior to the planting in the field.