Magnetic effect of ferritic steel board (FB) on the plasma was experimentally investigated in the JFT-2M tokamak. Clear deterioration by the error field was not observed even in the condition of toroidally unbalanced placement of FBs outside vacuum vessel (VV). Deteriorating effects were not observed with the FBs inside VV for the operational region and the control of plasma, although slight discrepancy in the relation of vertical-coil current and equilibrium was found. Compatibility of FBs with high normalized-beta plasma (βN up to 2.7) was demonstrated after boronization.