A sliding mechanism (100) for use in a portable electronic device (500) is provided. The sliding mechanism includes a first plate (10), a second plate (20), a plurality of limiting structure (17), and a linkage module (30). The second plate is longitudinally slidably connected with the first plate. The plurality of limiting structures is secured on the first plate for delimiting a position of the second plate with respect to the first plate. The linkage module is configured to approximate a collapsible hexagon and is disposed between and connects the first plate and the second plate. The linkage module further includes an elastic unit (34) that is able to semi-automatically drive the linkage module and enable the second plate to slide along the first plate, after the second plate is manually moved a predetermined length with respect to the first plate.