A mounting device (30) for a data storage device (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) and a retaining member (50). 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 (415) is formed on the bottom wall with a protrusion (416) formed thereon. The retaining member is slidably attached to the receiving member. The retaining member includes a base wall (51) and a retaining wall (53). At least one fixing pin (533) is formed on the retaining wall. An opening (511) is defined in the base wall corresponding to the protrusion.