The mutant with high productivity, X. malvacearum SNUF 560-6, was acquired from the X. malvacearum SNUF 560 with low productivity by UV-light irradiation. It was preserved is lyophilized stock culture and it was transferred to PDA slant to maintain viability fortnightly. Fermentations were started by retransfering to MY agar slant from PDA stok culture. The experiments for optimal xanthan gum production were studied in a chemically defined medium. Of the carbon and nitrogen sources tested, 0.4% sucrose medium and 10mM glutamic acid medium yielded the highest xanthan gun production respectively. The addition of 10g/l succinic acid stimulated xanthan gum production. Also 65mM $PO_4;^{-3};(12.6g/l;KH_2PO_4)$ was effective on xanthan gum production. Finally, medium 1 and medium 2 which have high xanthan gum production potencies were achieved in this stud. The components of medium 1 and medium 2 were as follows: Medium 1 : sucrose 40g/l glutamate 10mM $PO_4;^{-3};54mM;(KH_2PO_4;12.65g/l)$ Citrate 2g/l $MgSO_4{cdot}7H_2O;0.2g/l$ $H_3BO_3;0.005/l$ ZnO 0.006/l $FeCl_2{cdot}6H_2O;0.0024g/l$ $CaCO_3;0.02g/l$ Medium 2 : $Sucrose;40g/l;(NH_4)_2SO_4;2g/l$ $PO_4;^{-3};65mM;(KH_2PO_4;12.65g/l)$ Succinate 10g/l $MgSO_4{cdot}7H_2O;0.02g/l$ $H_3BO_3;0.06g/l$ ZnO 0.006g/l $FeCl_2{cdot}6H_2O;0.0024g/l$ $CaCO_3;0.02g/l$.