A casing structure including a frame having a capacity space and a fastener at a side of the capacity space that an electronic unit assembled therein, a first linking member slidably coupled to the frame, and a second linking member pivoted to the frame having a first and a second end is provided. The first end is linked to the first linking member and the second end faces to the electronic unit in the space. The electronic unit is locked by the fastener in assembling mode and the first linking member is located at a first position to block the fastener from releasing the electronic unit. The first linking member is forced to move out of the first position and drive the second linking member to rotate relative to the frame, such that the second end pushes the electronic unit to be released from the fastener in disassembling mode.