PROBLEM TO BE SOLVED: To provide a flush toilet bowl which can be flushed even during power failure without affecting the dirt discharge performance of ordinary toilet bowl washing.SOLUTION: A flush toilet bowl includes: a bowl part for receiving dirt; a drain trap part connected to the bowl part, discharging the dirt, and forming stored water in the bowl part; a drain socket connecting the downstream end of the drain trap part and the upstream end of a drain pipe to each other; and wash water supply means electrically driven by supply power and supplying wash water to the bowl part. The wash water supply means has water supply means which performs water supply and cutoff of wash water to the bowl part by any one of manual operation of a user, an emergency power source, and a mechanical element. The drain socket has opening and closing means which changes the sectional area of a drain socket channel by any one of manual operation of a user, an emergency power source, and a mechanical element during power fail
