A magnetic field measuring apparatus includes a cell array which includes plural cells different in size of detection surface through which a magnetic flux passes when the cells are arranged in a magnetic field of a measurement object, a medium which is enclosed inside each of the plural cells and rotates a light polarization plane according to an intensity of the magnetic field, an irradiator to irradiate a light to the detection surface of each of the cells, and a detector to detect a rotation angle of a polarization plane of the light passing through each of the cells.
