A tool position detection device comprising: a power feeding electrode provided on an inner wall of a tool attachment unit (5, 6, 55, 60) that attaches thereonto a tool (TP, TD) having a power receiving electrode and a displacement electrode, the power feeding electrode being provided to be opposite to the power receiving electrode in a longitudinal direction of the tool attachment unit (5, 6, 55, 60) in a non-contact state; a plurality of detection electrodes, which is provided on the inner wall to be opposite to the displacement electrode in a non-contact state, being insulated from the power feeding electrode, and being provided in line in the longitudinal direction of the tool attachment unit (5, 6, 55, 60); and a power feeding signal supply unit configured to supply an alternating current power feeding signal (Sfac) to the power feeding electrode, wherein, when the tool (TP, TD) is attached onto the tool attachment unit (5, 6, 55, 60), a pair of the power feeding electrode and the power receiving electrode, which are opposite to each other, and a pair of the detection electrode and the displacement electrode, which are opposite to each other, form a capacitor circuit (C31, C32), a capacity of the capacitor circuit (C31, C32) is configured to be changed in response to a position of the tool (TP, TD) with respect to the longitudinal direction of the tool attachment unit (5, 6, 55, 60), and the tool position detection device further comprises: a voltage information extractor configured to extract voltage information from the detection electrode when the power feeding signal (Sfac) is supplied to the power feeding electrode by the power feeing signal supply unit, the voltage information being changed in response to the capacity of the capacitor circuit (C31, C32); and a position detection/arithmetic operation unit configured to detect to which position in the longitudinal direction of the tool attachment unit (5, 6, 55, 60) the tool (TP, TD) is attached based on the voltage information extracted by the voltage information extractor. a power feeding electrode provided on an inner wall of a tool attachment unit (5, 6, 55, 60) that attaches thereonto a tool (TP, TD) having a power receiving electrode and a displacement electrode, the power feeding electrode being provided to be opposite to the power receiving electrode in a longitudinal direction of the tool attachment unit (5, 6, 55, 60) in a non-contact state; a plurality of detection electrodes, which is provided on the inner wall to be opposite to the displacement electrode in a non-contact state, being insulated from the power feeding electrode, and being provided in line in the longitudinal direction of the tool attachment unit (5, 6, 55, 60); and a power feeding signal supply unit configured to supply an alternating current power feeding signal (Sfac) to the power feeding electrode, wherein, when the tool (TP, TD) is attached onto the tool attachment unit (5, 6, 55, 60), a pair of the power feeding electrode and the power receiving electrode, which are opposite to each other, and a pair of the detection electrode and the displacement electrode, which are opposite to each other, form a capacitor circuit (C31, C32), a capacity of the capacitor circuit (C31, C32) is configured to be changed in response to a position of the tool (TP, TD) with respect to the longitudinal direction of the tool attachment unit (5, 6, 55, 60), and the tool position detection device further comprises: a voltage information extractor configured to extract voltage information from the detection electrode when the power feeding signal (Sfac) is supplied to the power feeding electrode by the power feeing signal supply unit, the voltage information being changed in response to the capacity of the capacitor circuit (C31, C32); and a position detection/arithmetic operation unit configured to detect to which position in the longitudinal direction of the tool attachment unit (5, 6, 55, 60) the tool (TP, TD) is attached based on the voltage information extracted by the voltage information extractor. a voltage information extractor configured to extract voltage information from the detection electrode when the power feeding signal (Sfac) is supplied to the power feeding electrode by the power feeing signal supply unit, the voltage information being changed in response to the capacity of the capacitor circuit (C31, C32); and a position detection/arithmetic operation unit configured to detect to which position in the longitudinal direction of the tool attachment unit (5, 6, 55, 60) the tool (TP, TD) is attached based on the voltage information extracted by the voltage information extractor.