Abstract: A casing structure includes a case member and a sliding member. The case member includes a first case body and a second case body. The sliding member includes a first slider, a second slider, and a torsion spring. The first case body and the second case body may move relative to each other through the sliding member. The first slider includes a hollow part and a spring fixing part extending from an edge of the hollow part into the first case body. The torsion spring includes a spiral portion. The two ends of the torsion spring are respectively disposed on the spring fixing part and the second slider, and the spiral portion of the torsion spring corresponds to the hollow part, thus reducing an overall thickness of the casing structure.