A shaft structure of a liftable screen cover includes a screen cover, a cover reinforcement plate and a shaft set. The side of the screen cover is formed with a bent sidewall. One end of the sidewall has a non-circular first hole. The cover reinforcement plate disposes inside the sidewall. One end of the cover reinforcement plate has a non-circular second hole. A fulcrum is formed between the sidewall of the screen cover and the cover reinforcement plate and connected in a male-and-female engagement. As a result, the fulcrum of the shaft can be greatly elongated. One end of the shaft center of the shaft set has a non-circular flange. The flange penetrates into the second hole and the first hole. Screws are used to fix the screen cover, the cover reinforcement plate and the shaft set. With the above arrangement, a structure has good rigidity and bears larger torsion.