A method for manufacturing a lanthanum oxide compound on a substrate includes: setting the number of H2O molecule, the number of CO molecule and the number of CO2 molecule to one-half or less, one-fifth or less and one-tenth or less per one lanthanum atom, respectively, the H2O molecule, the CO molecule and the CO2 molecule being originated from an H2O gas component, a CO gas component and a CO2 gas component in an atmosphere under manufacture; and supplying a metal raw material containing at least one selected from the group consisting of lanthanum, aluminum, titanium, zirconium and hafnium and an oxygen raw material gas simultaneously for the substrate under the condition that the number of O2 molecule are set to 20 or more per one lanthanum atom, thereby manufacturing the lanthanum oxide compound on the substrate.