An analytical method using capillary electrophoresis (CE) was developed for quantitation of water soluble vitamin contents in various vitamin products. The method includes the optimization of separation of 11 water soluble vitamins changing the micellar concentration and pH of running buffer, applied voltage and sample preparation. Best resolution was obtained with 25 mM phosphate buffer (pH=8.0) containing 50 mM sodium dodecyl sulphate (SDS) as micellar phase. At optimum condition, water soluble vitamins were determined in orange juice and vitamin products such as vitamin C pulvis, vitamin injection, coated multivitamin tablet. The quantitative analysis of water soluble vitamins with CE was suitable for quality control of pharmaceutical products with sound reproducibility.