Biomagnetic signals are very weak compared with those of the environment magnetic field due to train and motor car. The train especially the direct-current electric railcar is seemed to be one of the main urban magnetic noise sources at low frequency in Japan, by comparing the fluctuation of magnetic field at the day when there are many trains with that at the night when there is no train. In this paper, first, the relationship between the environmental magnetic field and the electric current of the direct-current electric railcar of the personal track was discussed. Second, the fluctuation of magnetic field was calculation from that of the unbalanced electric current between feeder line and railroad, which could be obtained as the leakage electric current to the ground. The validity of calculation was verified by comparison with measurements.