We produced transparent nanocomposite reinforced with bacterial cellulose having a wide range of fiber contents, from 7.4 to 66.1 wt %, by the combination of heat drying and organic solvent exchange methods. The addition of only 7.4 wt % of bacterial cellulose nanofibers, which deteriorated light transmittance by only 2.4%, was able to reduce the coefficient of thermal expansion of acrylic resin from 86x10(-6) to 38x10(-6) K-1. As such, the nanofiber network of bacterial cellulose has an extraordinary potential as a reinforcement to obtain optically transparent and low thermal expansion materials.