A slot-in type disk drive fastens a clamping unit with two protrusions around its periphery on the central hole of a base plate. A front positioning part utilizes a stick to link a front right positioning bar and a front left positioning bar to synchronously open or close. A locking rod has a limiting pin inserted into an arc slot on the side of the base plate, and protrudes a locking end from the rear end. A rear positioning part utilizes an idle gear to link rear right and rear left positioning bars to synchronously open or close. The locking end can insert a first or second positioning recess on the rear left positioning bar and a touch block of the locking rod leans against the first protrusion. A lever is disposed on the rear right positioning bar to link a linkage plate set by one end.