A linkage mechanism is configured between two relatively slidable first housing and second housing of a handheld device. The linkage mechanism can be actuated by a first actuator of the first housing when the second housing slides out at an opening status relative to the first housing. The linkage mechanism is actuated to rotate and then to drive a second actuator to slide on the second housing and the second actuator forces a supporter, which pivots to the second housing, to open at a predetermined angle relative to the second housing. The handheld device is made steady on a plane through the support provided by the opened supporter. When the handheld device slides in at a closing status, a restoring spring configured between the supporter and the second housing automatically folds the supporter.