A fastening device for fastening a data storage device includes a rack and a fastening member. The rack includes a bottom plate to support the data storage device, and two stop tabs protruding up from the bottom plate to abut against a first sidewall of the data storage device. Two first pins respectively extend from the stop tabs to engage in two corresponding holes defined in the first sidewall of the data storage device. The fastening member includes a main body attached to the bottom plate to abut against a second sidewall of the data storage device, and a resilient portion extending from the main body. A second pin protrudes from the resilient portion to engage in a locking hole defined in the second sidewall of the data storage device.