A mounting device (20) for a disk drive (80) has at least one retaining hole (81) defined in each one of two opposite sides thereof. The mounting device includes a receiving member (40), a retaining member (50), and a securing member (60). The receiving member includes a side wall (43) and a bottom wall (41). At least one fixing pin (433) is formed on the side wall. An elastic clip (413) is formed on the bottom wall with a protrusion (413) thereon. The retaining member is slidably attached to the receiving member. The retaining member includes a locking wall (51) and a retaining wall (53). At least one fixing pin (533) is formed on the retaining wall. The protrusion is engaged in an opening (511) defined in the locking wall. The securing member is attached to the retaining member. The securing member includes a pressing tab (613).