We describe an implementation of an algorithm for enumerating all maximal frequent sets using irredundant dualization, which is an improved version of that of Gunopulos et al. The algorithm of Gunopulos et al. solves many dualization problems, and takes long computation time. We interleaves dualization with the main algorithm, and reduce the computation time for dualization by as long as one dualization. This also reduces the space complexity. Moreover, we accelerate the computation by using sparseness.