A fixing mechanism for fixing a detachable module is disclosed. The fixing mechanism includes a cage having a first bent portion, and a sliding base installed inside the cage in a slidable manner for supporting the detachable module. The sliding base includes a rack, and at least one first resilient hook for engaging with the first bent portion when the sliding base is installed inside the cage so as to prevent the sliding base from separating from the cage in a first direction. The fixing mechanism further includes at least one spring module installed on the cage and engaged with the rack on the sliding base for driving the rack so as to slide the sliding base relative to the cage. The fixing mechanism further includes a latch module installed on the sliding base for latching the detachable module when the detachable module is installed inside the sliding base.