To solve the problems caused by power discharging from a noise filter and by resonance frequency current between the noise filter and earth capacitance.

The noise filter 10 of the present invention consists of a resistor 11 and an inductor 12 connected in parallel with each other. A power supply frequency current does not pass through the resistor 11 but passes through the inductor 12 with no loss. On the other hand, a high frequency noise current including a resonance frequency current, does not pass through the inductor 12 but is dissipated on the resistor 11. Therefore, the noise filter 10 can not store noise power and so does not suffer from a problem due to power discharging. The resonance frequency current caused by the noise filter 10 and the earth capacitance C is also dissipated at the resistor 11. Therefore, no problem is caused by the resonance frequency current.