A magnetic sensor element of a flux gate type comprising a magnetism sensitive part (8a) formed by winding a coil (3) around a magnetic core layer (8), and magnetism collective part (8b) for guiding magnetic fluxes to the magnetism sensitive part (8a). Respective central parts of the magnetism collective part (8b) are connected with the respective ends of the magnetism sensitive part (8a). Therefor the magnetic core layer (8) is formed so as to resemble a letter H in planar shape. And the coil (3) of the magnetism collective part (8b) is a thin-film coil comprising a plurality of upper coil thin-films (12) and a plurality of lower coil thin-films (4) formed on an upper surface and a lower surface of the magnetic core layer (8) via insulation layers by connecting together the respective lower coil thin-films (4) and the upper coil thin-films (12), at respective adjacent ends thereof, so as to be sequentially continuous with each other.