An electrostatic-coupling contactless power supply device (1, 1A, 1B) comprising: a plurality of power supply electrodes (21, 22); a power supply circuit that supplies power between the plurality of power supply electrodes; a plurality of power receiving electrodes (31, 32) that face the plurality of power supply electrodes (21, 22) so as to be spaced apart from the power supply electrodes (21, 22), and receive high-frequency power in a contactless manner; a power receiving circuit that converts the power received by the plurality of power receiving electrodes (31, 32) and supplies the converted power to an electrical load provided on the movable portion (3, 3A, 3B); and an electrode detecting section (4, 4A, 4B) that detects capacitances of capacitors (23, 24) formed by the power supply electrodes (21, 22) and the power receiving electrodes (31, 32) facing each other so as to be spaced apart from each other, and detects changes of the capacitances, characterized in that the electrode detecting section (4, 4A, 4B) includes a closed circuit (41, 41A) for detection that includes the capacitors (23, 24) and does not include the power supply circuit and the electrical load, an AC signal source (42, 42A) that is provided in the closed circuit (41, 41A) for detection and outputs an AC signal having a detection frequency different from a power supply frequency obtained when the power supply circuit supplies the power, a filter unit that is provided in the closed circuit (41, 41A) for detection, allows the AC signal having the detection frequency to pass therethrough, and blocks a signal having the power supply frequency, and a detector that is provided in the closed circuit (41, 41A) for detection and detects the AC signal having the detection frequency. a plurality of power supply electrodes (21, 22); a power supply circuit that supplies power between the plurality of power supply electrodes; a plurality of power receiving electrodes (31, 32) that face the plurality of power supply electrodes (21, 22) so as to be spaced apart from the power supply electrodes (21, 22), and receive high-frequency power in a contactless manner; a power receiving circuit that converts the power received by the plurality of power receiving electrodes (31, 32) and supplies the converted power to an electrical load provided on the movable portion (3, 3A, 3B); and an electrode detecting section (4, 4A, 4B) that detects capacitances of capacitors (23, 24) formed by the power supply electrodes (21, 22) and the power receiving electrodes (31, 32) facing each other so as to be spaced apart from each other, and detects changes of the capacitances, characterized in that the electrode detecting section (4, 4A, 4B) includes a closed circuit (41, 41A) for detection that includes the capacitors (23, 24) and does not include the power supply circuit and the electrical load, an AC signal source (42, 42A) that is provided in the closed circuit (41, 41A) for detection and outputs an AC signal having a detection frequency different from a power supply frequency obtained when the power supply circuit supplies the power, a filter unit that is provided in the closed circuit (41, 41A) for detection, allows the AC signal having the detection frequency to pass therethrough, and blocks a signal having the power supply frequency, and a detector that is provided in the closed circuit (41, 41A) for detection and detects the AC signal having the detection frequency.