The utility model relates to an open-close device for the pedal controller of a flush toilet, comprising an open-close ring, an upper cover ring, a lower cover ring and a shaft which are driven by a rotating mechanism. The open-close ring is provided with an eccentric slot. A balance wheel is installed in the eccentric slot. One side of two sides of the balance wheel is matched with a flat slot of the upper cover ring. The other side of the balance wheel is matched with the shallow slot and the deep slot of a secondary open-close slot. The utility model is capable of driving the cover and the seat ring of the flush toilet to be opened and closed in turn by the open-close ring rotating, solves the key problem of the technique of switching the gear, realizes the use of the pedal controller for replacing the hands to open and close the flush toilet and reaches the purposes of sanitation and convenient use.