AbstractWith the widespread use of various electrical applicances in daily life, there has been an increase in unnecessary radiated electromagnetic waves influencing many spheres of social life. In addition to the radiation of unnecessary electromagnetic waves by electrical machinery, considerable noise arises from ignition systems of internal combustion engines. We assumed that the sources of electromagnetic waves were always due to the flow of radio wave currents. As an example of internal combustion engines, this paper uses an automobile engine. Also, a surface current detector was used for the generated noise currents (in the 300‐MHz band). By means of measurements over the body of an automobile (sedan type), the relationship between the noise currents and the radiated noise waves was examined. The automobile body receives various electromagnetic waves which exist in space, especially TV waves, and that flow as high‐frequency currents all over the automobile body. Naturally the reradiation if these waves is considered. On the other hand, a large amount of noise currents of the engine system flows on the bonnet near the fender part. It was observed especially that the noise currents tended to flow from the top of the ignition coil inside the engine housing. However, no noise currents were observed on the car door, roof and trunk. Based on these measurements of the radio noises actually radiated, it can be inferred that it is possible to reduce the electromagnetic radiation if the noise currents which are flowing in the bonnet and the fender part are eliminated.