To demonstrate the different vibration characteristics of a magnetic spring compared with those of a metal one, a magnetic spring apparatus was constructed from a pair of circular magnets of the same size with an inside diameter of 2.07 cm and an outside diameter of 4.50 cm. To keep the upper magnet in a suspension state, the two magnets were placed vertically on a ceramic rod, with the same polarity sides facing against one another. The variation of magnetic field, resulting from the oscillation of the upper magnet, was recorded online with the aid of a magnetic field sensor and a data acquisition computer. It showed that the repulsion force has a nonlinear dependence on the gap between the two magnets in the form of a polynomial of power series. (Contains 1 table and 8 figures.)