A hard disk fixing mechanism includes a casing, a partitioning member, a fixing feature, a plurality of studs and a number of position-limiting slots. The casing has two plates. The partitioning member is connected to the plates to define two accommodating areas for accommodating hard disks. These studs are respectively located on the plates. These position-limiting slots are respectively formed on two opposite sides of the partitioning member so that the studs are removably buckled on the position-limiting slots. The fixing feature is able to fix the partitioning member to the casing to prevent the studs from being disengaged from the position-limiting slots.