The electrostatic fluctuation was observed by a heavy ion beam probe (HIBP) at the central cell in the GAMMA 10 tandem mirror. The fluctuation of the end plates settled at both side of GAMMA 10 was observed. In the plasma, as increasing of the electrostatic fluctuation, decrease of the diamagnetism and electron density was observed. The radial profile of particle transport induced by fluctuations increased substantially. A strong correlation between the potential fluctuations measured by HIBP and end plates was observed. The electrostatic fluctuation propagated from the central cell to end cell.