Electrochemical intercalation of a variety of organic cations such as alkylammonium, anilinium and alkylpyridinium ions including rhodamine 6G into layered oxide, MoO3 were examined. Cyclic voltammetry indicated that redox potentials of MoO3 depends on the kinds of organic electrolytes. The electrochemical intercalation method could be applied to MoO3 thin film deposited onto transparent electrode. Interlayer spacing of MoO3 measured by XRD increased from an intial value of 6.9 Angstrom to an intercalated value in the range of 10-19 Angstrom, and reduction of MoO3 was confirmed by XPS measurement.