A slot-in optical disk drive includes a holding mechanism, a main body and a sliding module. The holding mechanism includes a disk slotting opening, two sliding rails and two slope rails. The main body and the sliding module are held by the holding mechanism. The main body includes a shelf, a disk reading unit and a main spindle motor. The sliding module includes a sliding base, two clamp sheets and a driving unit, each clamp sheet having a pivot end, a free end opposite to the pivot end and a sliding block. If the sliding block is at the sliding rail, the free end of the clamp sheet and the sliding base are closed up; and if the sliding block is at the slope rail, the free end of the clamp sheet and the sliding base are opened up.