A mounting device for a heat sink (200) includes a pair of pivot members
(10), two joining members (30), and two pairs of spring members (20).
Each pivot member includes a clipping portion (11) for clasping the
electric unit (300). The joining members pivotably connect with the pivot
members. Each joining member includes a pressing portion (310) for
resiliently abutting against the heat sink toward the electric unit. The
spring members each includes two end catches (21), (22) secured with the
joining member and a corresponding member and capable of providing
resilient torsions to drive the clipping portions to engage with the
electric unit when the clipping portions rotate to one position away from
the electric unit.