To obtain a magnetic sensor comprising a thin and long magnetic core and a coil wound around the magnetic core and detecting a magnetic field based on the variation in the inductance of coil wherein sensitivity is enhanced without increasing the number of turns of coil.

The number of turns of a coil 2 is set higher in the central part of a magnetic core 1 than at the end part thereof. Consequently, the bias field induced by a bias current flowing through the coil 2 is applied efficiently to the magnetic core 1. According to the structure, inductance of the coil 2 can be set at a high value without increasing the number of turns and high sensitivity can be attained.