To provide a flush toilet bowl capable of being reduced in size and being washed satisfactorily.

The flush toilet bowl includes a toilet bowl body 10 having a toilet pot 11, a toilet bowl drain channel 12 communicating with a downstream of the toilet pot 11 and an upper face 13 adjacent to an upper end peripheral edge of the toilet pot 11 to be extended backward, a toilet bowl washer 20 arranged at an upper side of a rear end of the toilet bowl body 10, and a suction device 30 for sucking air into the toilet bowl drain channel 12. The toilet bowl body 10 has a cavity 40 formed at a front side of the toilet bowl washer 20, at a rear side of the toilet pot 11, at an under side of the upper face 13, and at an upper side of the toilet bowl drain channel 12. A lower end of the cavity 40 is opened toward an upper end of the toilet bowl drain channel 12, and an upper part thereof communicates with a suction passage 31 of the suction device 30.