An automatic tonearm lifter adapted for use in a turntable, the turntable including a main body, and a tonearm that is rotatably mounted on the main body, said automatic tonearm lifter comprising: a casing that is adapted to be fixedly mounted to the main body of the turntable; a lifting unit that is mounted to said casing, that is adapted for supporting the tonearm, that is movable relative to said casing along a vertical axis, and that is non-rotatable about the axis relative to said casing; a rotating unit that includes a threaded seat rotatable about the axis and threadably engaging said lifting unit, and a driving module connected to said threaded seat and being operable to drive rotation thereof, said rotating unit being configured to move said lifting unit along the axis; and a control unit that is coupled to said driving module of said rotating unit, that is configured to control operation of said driving module, and that includes a control module signally connected to said driving module, and a lifting unit sensing module signally connected to said control module and configured to sense displacement of said lifting unit relative to said casing; wherein said lifting unit sensing module includes two first sensing members that are spaced apart along the axis, and a second sensing member that is mounted to said lifting unit and that is configured to sense presence of either one of said first sensing members; and wherein when said second sensing member is configured to sense presence of either one of said first sensing members, said lifting unit sensing module is configured to generate a lifting unit sensing signal and to send the lifting unit sensing signal to said control module to stop operation of said driving module; said automatic tonearm lifter being characterized in that: each of said first sensing members of said lifting unit sensing module is one of a magnetic member and a hall device that is signally connected to said control module, and said second sensing member is the other one of the hall device and the magnetic member. a casing that is adapted to be fixedly mounted to the main body of the turntable; a lifting unit that is mounted to said casing, that is adapted for supporting the tonearm, that is movable relative to said casing along a vertical axis, and that is non-rotatable about the axis relative to said casing; a rotating unit that includes a threaded seat rotatable about the axis and threadably engaging said lifting unit, and a driving module connected to said threaded seat and being operable to drive rotation thereof, said rotating unit being configured to move said lifting unit along the axis; and a threaded seat rotatable about the axis and threadably engaging said lifting unit, and a driving module connected to said threaded seat and being operable to drive rotation thereof, said rotating unit being configured to move said lifting unit along the axis; and a control unit that is coupled to said driving module of said rotating unit, that is configured to control operation of said driving module, and that includes a control module signally connected to said driving module, and a lifting unit sensing module signally connected to said control module and configured to sense displacement of said lifting unit relative to said casing; wherein said lifting unit sensing module includes two first sensing members that are spaced apart along the axis, and a second sensing member that is mounted to said lifting unit and that is configured to sense presence of either one of said first sensing members; and wherein when said second sensing member is configured to sense presence of either one of said first sensing members, said lifting unit sensing module is configured to generate a lifting unit sensing signal and to send the lifting unit sensing signal to said control module to stop operation of said driving module; said automatic tonearm lifter being characterized in that: each of said first sensing members of said lifting unit sensing module is one of a magnetic member and a hall device that is signally connected to said control module, and said second sensing member is the other one of the hall device and the magnetic member.