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 (21, 22) 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 (21, 22); two electrodes (24, 25) for wire energization, connection parts (26, 27) between the two conductive magnetic wires (21, 22) and the electrodes (24, 25) for wire energization, a detection coil wound around the two conductive magnetic wires (21, 22), two electrodes (34, 35) for coil voltage detection, a connection part between the coil and the two electrodes (34, 35) for coil voltage detection, wherein the two conductive magnetic wires (21, 22) 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 (24, 25) 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 (21, 22), and an insulating separation wall is arranged between the two conductive magnetic wires (21, 22). wherein the magnetic field detection element comprises two conductive magnetic wires (21, 22) 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 (21, 22); two electrodes (24, 25) for wire energization, connection parts (26, 27) between the two conductive magnetic wires (21, 22) and the electrodes (24, 25) for wire energization, a detection coil wound around the two conductive magnetic wires (21, 22), two electrodes (34, 35) for coil voltage detection, a connection part between the coil and the two electrodes (34, 35) for coil voltage detection, wherein the two conductive magnetic wires (21, 22) 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 (24, 25) 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 (21, 22), and an insulating separation wall is arranged between the two conductive magnetic wires (21, 22).