In this study, the body force field of a DBD plasma actuator is investigated using the three-dimensional numerical simulation of the discharge plasma behavior. The streamer-type and the glow-type discharges as observed in a previous experimental study are successfully simulated by attaching small bumps to the exposed electrode edge. The space scale of the streamer is from several tens to several hundreds micro meters. The glow-type discharge plasma is more diffusive, and its space scale is up to one mili meters. In the streamer-type discharge phase, small branching of the discharge pass appears, however, the structure of the discharge branch strongly depends on the grid resolution. The simulation results showed that the body force field spatially and temporally varies coincident with the discharge plasma evolution; the space non-uniformity of the body force field is in the same space scale of the discharge plasma, and cannot be ignored within a time scale of not less than several tens micro seconds (several voltage cycles).