Non-contact electrical power transmission system having function of making load voltage constant

This system includes a transformer separable/detachable between a primary winding and a secondary winding, and a capacitor connected parallel to the secondary winding of the above-mentioned transformer, and supplies a high-frequency AC voltage to the primary winding of the transformer to generate an induced voltage in the secondary winding of the transformer, and transmits the electrical power to a load in non-contact manner. The voltage supplied to the load is constant and the flowing current varies. The power may be supplied to a different kind of a load with a constant voltage. Taking as a first condition a fact that at the time of a maximum load, the time of the reversal of the voltage polarity of the above-mentioned primary winding substantially coincides with the time when an oscillating voltage of the above-mentioned capacitor reaches a maximum or minimum value, and taking as a second condition a fact that at the time of a minimum load, the time of the reversal of the voltage polarity of the above-mentioned primary winding substantially coincides with the time when the oscillating voltage of the above-mentioned capacitor completes one cycle, the above-mentioned capacitor is set so that the capacity value satisfies simultaneously the above-mentioned first and second conditions. This allows the load voltage to be made constant in a load current range from a minimum to a maximum without requiring a feedback circuit.