We fabricated an ordered monolayer film of a long-chain fatty acid or a perfluorofatty acid onto an anodized tantalum oxide (Ta2O5) amorphous surface by the Langmuir-Blodgett (LB) method, and grew a pentacene or C-60 thin film on it. Remarkable improvements of morphology and crystallinity of the organic thin films were observed on the CH3-terminated monolayer film of the fatty acid.