A holding device for a heat sink being attached to a circuit board includes a back plate and a frame member. The back plate provides a plurality of fixing posts with a free end of the respective fixing post having a neck recess piecing the circuit board and each of the fixing posts being surrounded with a spring. The frame member provides a plurality of corners with a support leg vertically extending from the corners respectively and a first flat fixing ear horizontally extending outward from the corners. The first fixing ear has a first elongated hole with a first end part for being pierced by the fixing post and a second end part for fitting with the neck recess. The first elongated hole extends from the first end part to the second end part in a way of allowing the frame member being moved along a direction before the second end part fitting with neck recess.