An exemplary pressing device (100) includes a first movable member (10) and a second movable member (20). Each of the first and second movable members includes an upper clamping element (11, 21) and a lower clamping element (12, 22). The upper clamping element has a first fringe portion and a plurality of first latching grooves (111, 211) having different sizes are defined in the first fringe portion. The lower clamping element has a second fringe portion and a plurality of second latching grooves (121, 221) having different sizes are defined in the second fringe portion. Each first latching groove of the second movable member has a same size as that of a corresponding first latching groove of the first movable member. Each second latching groove of the second movable member has a same size as that of a corresponding second latching groove of the first movable member.