An ultra-small and high-sensitivity magnetic sensor comprising: an application specific integrated circuit ASIC ; an insulating protective film formed on a wiring plain surface of the ASIC ; a substrate film having a groove ; and a magnetic field detection element , wherein the magnetic field detection element comprises two conductive magnetic wires arranged adjacent and parallel to one another, and fixed in the groove , a wire coupling part connecting a lower end of one magnetic wire and a lower end of the other magnetic wire of the two conductive magnetic wires ; two electrodes for wire energization, connection parts between the two conductive magnetic wires and the electrodes for wire energization, a detection coil wound around the two conductive magnetic wires , two electrodes for coil voltage detection, a connection part between the coil and the two electrodes for coil voltage detection, wherein the two conductive magnetic wires have conductivity and an anisotropic magnetic field of 20 G or smaller, and have a two-phase magnetic domain structure of a surface magnetic domain having spin alignment in a circumferential direction, and a central core magnetic domain having spin alignment in an axial direction, and are fixed and covered by an insulating resin , and the detection coil has a coil pitch of 10 μm or smaller, characterized in that , the substrate film is formed on the insulating protective film , the electrodes for wire energization are directly jointed to an element coupling electrode of the ASIC passing through the substrate film and the insulating protective film , and in the magnetic field detection element , a lower part of the detection coil is formed along the groove surface of the groove and both sides of the groove formed on the substrate film , an upper part of the detection coil is provided on the insulating resin , the detection coil is wound around the two conductive magnetic wires , and an insulating separation wall is arranged between the two conductive magnetic wires . wherein the magnetic field detection element comprises two conductive magnetic wires arranged adjacent and parallel to one another, and fixed in the groove , a wire coupling part connecting a lower end of one magnetic wire and a lower end of the other magnetic wire of the two conductive magnetic wires ; two electrodes for wire energization, connection parts between the two conductive magnetic wires and the electrodes for wire energization, a detection coil wound around the two conductive magnetic wires , two electrodes for coil voltage detection, a connection part between the coil and the two electrodes for coil voltage detection, wherein the two conductive magnetic wires have conductivity and an anisotropic magnetic field of 20 G or smaller, and have a two-phase magnetic domain structure of a surface magnetic domain having spin alignment in a circumferential direction, and a central core magnetic domain having spin alignment in an axial direction, and are fixed and covered by an insulating resin , and the detection coil has a coil pitch of 10 μm or smaller, characterized in that , the substrate film is formed on the insulating protective film , the electrodes for wire energization are directly jointed to an element coupling electrode of the ASIC passing through the substrate film and the insulating protective film , and in the magnetic field detection element , a lower part of the detection coil is formed along the groove surface of the groove and both sides of the groove formed on the substrate film , an upper part of the detection coil is provided on the insulating resin , the detection coil is wound around the two conductive magnetic wires , and an insulating separation wall is arranged between the two conductive magnetic wires . <EOS>