Provided is a feed line structure that enables suppression of noise entering a primary power supply from an electronic circuit without using a circuit component such as a choke coil and a capacitor and also without increasing an occupied area on the circuit board, so that an EMI countermeasure is achieved. The feed line structure includes a feed line composed by pairing a power supply wire 41 and a reference potential wire 42 in an insulator 40, and is characterized in that a wire 43 in a floating state in potential is provided.