One of biopolymer, curdlan, was mixed with concrete to enhance the fluidity and to increase the strength of concrete. Using powder type of curdlan, its effect on fluidity was very low relative to that of welan due to solubility during mixing. To increase the solubility of curdlan, small amount of NaOH was added. As a result, the fluidity of concrete was greatly improved with NaOH addition and the strength of concrete was also improved. The optimal pH of dissolving solution for the best quality concrete was pH 12.7. The pilot scale experiment also showed good performance in the slump value and also in concrete strength. From these experiments, we can approve that curdlan produced from microorganism is a good super plasticizer for concrete mixture.