A locking device includes a flat plate for contacting with a heat-generating electronic component, a plurality of fins mounted on the flat plate, four locking feet and four fasteners. The flat plate includes two locking portions at opposite sides thereof. Each locking foot includes two spaced pivot plates at an end thereof, wherein the locking portions of the flat plate are sandwiched between the pivot plates. The locking feet are pivotably connected to the locking portions. The fasteners are secured to ends of the locking feet respectively, opposite to the ends where the spaced pivot plates are formed. The locking feet are pivotably movable between first and second positions. The locking device can be mounted to a first-typed PCB at the first position and a second-typed PCB at the second position.