A portable device has lower and upper casings. A sliding hinge has a stationary frame attached to the lower casing, a sliding frame attached to the upper casing and a resilient positioning assembly mounted between the stationary and sliding frames. The sliding frame has multiple pushing pins protruding toward the stationary frame. The resilient positioning assembly has two sliders and multiple resilient elements disposed between and abutting the sliders. When the upper casing slides relative to the lower casing, the pushing pins move along and push corresponding sliders and pressing the resilient elements. As long as the pushing pins are moved to the other sides of the corresponding sliders, the resilient elements push the sliders back and the upper and lower casings of the portable device are open relative to each other.