A flush driving device for a toilet includes a mounting bracket, a control panel that includes a sensing window and manual buttons, and a manual operating mechanism that includes bars cooperating with the manual buttons and rotating mechanisms connected with the bars. Rotating shafts of the rotating mechanisms are mounted in the mounting bracket. An automatic operating mechanism includes a driving motor, a rod controlled by the driving motor, and lifting mechanisms cooperating with the rod. The flush driving device also includes pull arms connected to both the rotating mechanisms and the lifting mechanisms for controlling the flush of the toilet.