To improve the performance of ice energy storage systems, the problem of freezing on the cooling surface must be addressed. One of the authors has proposed a new ice-making method in which a magnetic fluid prevents water from freezing on the cooling surface. Thus, we investigated experimentally the effect of shape control of magnetic fluid using a magnet on the supercooling phenomenon. The changes of the degree of supercooling and the heat flux with time are shown for several cases. The shape changes and motion of magnetic fluid, which are controlled by controlling the magnetic field, have a slight effect on the supercooling phenomenon. However, exposure of the cooling surface covered by a film of magnetic fluid reduces the critical degree of supercooling.