Rotation of a Field-Reversed Configuration (FRC) plasma due to a resistive flux decay is numerically studied. When the anomaly factor is 10, the flux lifetime is found to be about 60 sec in a case that the external magnetic field is O.4 T and the wall radius is 0.17 m. Single-particle motions in a quasi-steady resistively decaying FRC equilibrium are calculated, and a local flow velocity is estimated by a particle-in-cell method. An electric acceleration of a betatron particle near the field-null is shown; this can cause a plasma rotation. From a comparison of the toroidal ion flow velocity profile between with and without the flux decay, it is found that the ion rotation begins at the field-null.