The present invention relates to a cover for a toilet bowl comprising: a rotary flange formed at a rear portion; a cover member rotatably coupled to the rotary flange; a toilet seat to which the cover member is coupled; a rotary support panel coupled to the toilet bowl and having a spherical rotary guide groove formed therein; a rotary member coupled to the rotary support panel so as to rotate and connecting the cover member and the toilet seat to the toilet bowl; a rotary assembly provided at the rear of the toilet seat and connected to an end of the rotary member to rotate the rotary member when the positions of the toilet seat and the cover member have been changed; and a water flushing device for operating a water flushing means by using a rotational force.