PROBLEM TO BE SOLVED: To provide a magnetism sensor which measures a faint magnetic flux induced, for example, by a faint electric current generated in a living body, and can reduce effectively an environmental magnetic field at the early stage for inputting, thereby to improve the S/N ratio.SOLUTION: The magnetism sensor uses a pair of magnetism detective elements 301a and 302a which have their respective strong magnetic materials and are equivalent to each other, wherein the elements are arranged in parallel to a detection magnetic flux B and further have a space between them along the direction of the detection magnetic flux B so that magnetizable axes 3011a and 3021a may intersect the detection magnetic flux B at right angles and be mutually orthogonal. Therefore, almost equal magnetic fluxes (five strings in Figure) are inputted to the environmental magnetic field (external magnetic fluxes) BN such as the geomagnetism arriving widely and uniformly, while signal magnetic fluxes BS (nine strings in the Figure) originated from the living body are absorbed into the element 301a nearer to the living body and dispersed from the outlet of a magnetic permeable route. Consequently, differential motion in output between the elements 301a and 302a can be used to reduce the environmental magnetic field efficiently, thereby to improve the S/N ratio.
