Caffeic acid was glucosylated with hydroquinone glucosylating enzyme (HGE) from Bacillus subtilis X-23 in order to improve its characteristics. Caffeic acid glucosides were found to be produced effectively from maltopentaose and caffeic acid in 30% ethanol solution. The glucosides were isolated from the reaction mixture by successive chromatography on DIAION HP-20, Sephadex G-10, and octadecyl sililated silica gel, following which two kinds of glucosides were obtained. The structures of these glucosides were confirmed to be caffeic acid 3-O-alpha-glucopyranoside and caffeic acid 4-O-alpha-glucopyranoside by H-1-NMR and C-13-NMR. The solubility of caffeic acid in water was increased by glucosylation without the loss of any biological activity, such as its antioxidative and antimutagenic properties.