A combination of electrolyzed acidic water (EAW) and ultrasonic vibration treatments or an alcohol treatment was performed to examine bactericidal effects on the Japanese hornwort (Cryptotaenia japonica Hassk.). Disinfection of Japanese hornwort leaves by EAW alone or combined treatment with EAW and ultrasonic vibration did not affect their appearance or chlorophyll content. The treatment with EAW alone showed some bactericidal effect, and the combined treatment with EAW and ultrasonic vibration (30 seconds) increased the effectiveness. Longer ultrasonic vibration for 5 minutes provided an effect that was similar to the effect of 30-sec. treatment. Bactericidal effect with80% ethanol solution was almost equivalent to that of the combined treatment with EAW and ultrasonic vibration. The bacterial counts were reduced when a suspension of a leaf in water was diluted by 50-fold or more of EAW or 5-fold or more of ethanol. This result showed that EAW or ethanol failed to fully disinfect Japanese hornwort leaves because these disinfectants did not have direct contact with microorganisms inside the leaves. In addition, EAW treatment was effective not only in disinfection but also in reduction of water loss from Japanese hornwort leaves during storage.