PURPOSE: To provide the method for manufacturing a fine ferroelectric epitaxial thin film having the smooth surface and less impurities.

CONSTITUTION: In the method for manufacturing a ferroelectric epitaxial thin film by a chemical vapor growth method, one or more kinds of alkoxide of lithium or β-diketone-based metal coupler and one or more kinds of alkoxide of niobium and tantalum or each β-diketone-based metal coupler are used as the vapor-phase raw materials. These gases are introduced into a reacting device with inert carrier gas. The raw material gas is oxidized by oxidizing material such as oxygen. Thus, Li(TaxNb1-x)O3 (0≤x≤1) thin film is formed on a LiTaO3 or LiNbO3 substrate at the substrate temperature of 700-900°C. The substrate temperature is made relatively high. Thus, the mixing of impurities is less, crystal defects such as sputtering damages in a sputtering method is less and the epitaxial thin film having the excellent interface state with the substrate is obtained.