A portable disk device includes a protective housing with a containing room and a portable disk disposed inside the containing room via a movable pivot means. The portable disk can be rotated between the retraction and first positions. A torsion means is included to interact with the portable disk and the movable pivot means to store potential energy. A movable component is used to interact with interaction portions to make the portable disk able/unable to have a movement relative to the protective housing. At the retraction position, the portable disk is positioned inside the containing room and the torsion means has the potential energy to slide out the portable disk. After the interaction between the movable component and the interaction portions is released, the portable disk is slid out. Afterward, the portable disk can be placed at the second position and only has the electrical connector being placed outside.