  The von Neumann entanglement entropy is studied with the density-matrix
renormalization group technique. We propose a simple approach to calculate the
central charge using the entanglement entropy for one-dimensional (1D) quantum
system. This approach is applied to a couple of quantum systems: (i) 1D
frustrated spin model and (ii) 1D half-filled spinless fermions with
nearest-neighbor repulsion; and, it is confirmed that the central charge is
estimated very accurately for the both systems. Also, a new method to determine
the critical point between TL-liquid and gapped (or ordered) phases from the
proposed approach is suggested. Furthermore, we mention that the
Tomonaga-Luttinger parameter can be obtained in a like manner as the central
charge, using the charge-density fluctuation of a part of the 1D system.
