Vibration of square and rectangular plates was discussed by W. Ritz, S. Tomotika, S. Iguchi, D. Young and M. V. Barton. Vibrations of clamped parallelogramic flat plates with aspect ratios 1 and 1/2 was discussed by the author. In this paper, we shall calculate the smallest frequency of the vibration of clamped parallelo-grammic isotropic flat plates with aspect ratio 1/4.