Previously proposed procedure for improving the effective potential by using renormalization group equation (RGE) is generalized so as to be applicable to any system containing several different mass scales. If one knows L-loop effective potential and (L + 1)-loop RGE coefficient functions, this procedure gives an improved potential which satisfies the RGE and contains all of the leading, next-to-leading, …, and L-th-to-leading log terms. Our procedure here also clarifies how naturally the so-called effective field theory can be incorporated in the RGE in \overlineMS scheme.