The invention relates to a device for measuring continuous magnetic fields, which is based on manganese mixed oxides having a perovskite structure. The inventive device, which is based on La-Ca-Sr-Mn mixed oxides with a perovskite structure, can detect continuous magnetic fields with intensities of between 0 and 9 T and measure the intensity, with an accuracy of 1Oe (1 T = 10,000 Oe), and orientation thereof, all within a wide temperature range. The sensor element of the device consists of a cylindrical wafer having a thickness that is at least of a smaller order of magnitude than the diameter thereof and comprising mixed oxide with a controlled quantity of cation vacancies in the sub-network A of same. The electric resistance of said material varies considerably as a function of the magnetic field applied.