Abstract: The present invention relates to an apparatus and a method for treating cancer using a discontinuous fractional alternative electric field, and more particularly, to an apparatus and a method for treating cancer using a discontinuous fractional alternative electric field capable of providing the same treatment effect on tumor while minimizing an effect on normal tissues by reducing time for which an electric field is applied over the existing electric field treatment. According to the exemplary embodiments of the present invention, the discontinuous fractional alternative electric field shows the same effect as applying the continuous electric field to the cancer cells while reducing the effect on the normal cells, and as a result the method for treating cancer using an optimized alternative electric field may be constructed by the treatment using the discontinuous fractional alternative electric field.