A substrate working machine for performing predetermined work on a substrate and that comprises a static portion , a movable portion movably mounted on the static portion, means for driving the movable portion using a linear motor device or a ball screw feed mechanism, and an electrostatic-coupling contactless power supply device comprising: a plurality of power supply electrode plates that are provided on the static portion; a high-frequency power source circuit that is configured to supply high-frequency power between the plurality of power supply electrode plates; a plurality of power receiving electrode plates that are provided on the movable portion, face the plurality of power supply electrode plates so as to be spaced apart from the plurality of power supply electrode plates, respectively, and are configured to receive high-frequency power in a contactless manner; and a power receiving circuit that is configured to convert the high-frequency power received by the plurality of power receiving electrode plates and is configured to supply the converted high-frequency power to an electrical load provided on the movable portion, wherein, capacitances of a plurality of capacitors, which are formed by the power supply electrode plates and the power receiving electrode plates facing each other so as to be spaced apart from each other, are changed so as to compensate each other and thus suppress a change of a resonant frequency of a resonant circuit when the position of the movable portion relative to the static portion is changed, and characterized in that the high-frequency power source circuit is configured to variably adjust an output frequency of the high-frequency power in accordance with the resonant frequency and configured to suppress a difference generated between the output frequency and the resonant frequency and configured to perfom contactless power supply using the resonant circuit. a plurality of power supply electrode plates that are provided on the static portion; a high-frequency power source circuit that is configured to supply high-frequency power between the plurality of power supply electrode plates; a plurality of power receiving electrode plates that are provided on the movable portion, face the plurality of power supply electrode plates so as to be spaced apart from the plurality of power supply electrode plates, respectively, and are configured to receive high-frequency power in a contactless manner; and a power receiving circuit that is configured to convert the high-frequency power received by the plurality of power receiving electrode plates and is configured to supply the converted high-frequency power to an electrical load provided on the movable portion, wherein, capacitances of a plurality of capacitors, which are formed by the power supply electrode plates and the power receiving electrode plates facing each other so as to be spaced apart from each other, are changed so as to compensate each other and thus suppress a change of a resonant frequency of a resonant circuit when the position of the movable portion relative to the static portion is changed, and characterized in that the high-frequency power source circuit is configured to variably adjust an output frequency of the high-frequency power in accordance with the resonant frequency and configured to suppress a difference generated between the output frequency and the resonant frequency and configured to perfom contactless power supply using the resonant circuit. <EOS>