A locking device (10) for securing a heat sink (20) to a heat generating component (30) includes a pair of operating members (14) and a pair of locking members (16). Each operating member includes a pivot shaft (142) defining an axis and an operation handle (144) extending from the pivot shaft along a first direction. The pivot shaft has an offset section (146) offsetting from the axis thereof in a second direction. The first direction and the second direction form an angle therebetween. Each locking member is attached to the offset section of one of the operating members. The operation handle of each operating member is capable of rotating about the axis of the pivot shaft from an unlocked position to a locked position and accordingly the offset section of the pivot shaft drives the locking member to move upwardly.