Two dimensional electrostatic particle simulation was done to simulate the extraction of negative ions from the plasma including electrons, ions, and negative ions. The simulation system consists of walls, plasma region, vacuum region, various electrostatic grids such as plasma grid, extraction grid, and acceleration grid. There is a external magnetic field in the extraction grid region. Full dynamics of charge particles are followed. It is shown that the modeling of source region is crucial to approach the stationary state. Only negative ions are successfully accelerated to the acceleration grid if the various parameters are properly chosen. Selfconsistent effects such as sheath formation, space charge effect, the shape of plasma‐vacuum boundary are found to be important for the extraction of negative ions.