An adjustable docking device includes a hinge mechanism, a holding base, a guiding member, and a fixing mechanism. The hinge mechanism is installed on a frame. The holding base is pivoted to the frame by the hinge mechanism. The holding base includes a main casing, a first holding casing and a second holding casing. The first holding casing and the second holding casing respectively extends from the main casing. The main casing, the first holding casing, and a second holding casing cooperatively define a clamping slot for holding an electronic device. The guiding member is disposed inside the clamping slot and for guiding the electronic device into the clamping slot. The fixing mechanism is disposed inside the holding base and capable of switching between a locking status and a releasing status, so as to lock or release the electronic device.