Abstract: There is provided a method of producing a separation membrane in which a zeolite membrane is formed on an inorganic oxide porous substrate. The substrate has amorphous SiO2 as a main component of a zeolite formation portion of the substrate, the method includes: a first step of forming a zeolite seed crystal and an alkaline component including a structure directing agent on a surface of the substrate; and a second step of treating a formed product obtained in the first step under a heated steam atmosphere, and the zeolite membrane is formed on the surface of the substrate.

Abstract: There is provided a zeolite membrane which is an MFI-type zeolite membrane formed on an inorganic oxide porous substrate, in which, in a diffraction pattern obtained by X-ray diffraction measurement using a CuK? ray as an X-ray source, when an intensity of a diffraction peak appearing at diffraction angles of 7.3° to 8.4° at which a crystal lattice plane belongs to 011 and/or 101 planes is used as a reference, an intensity of a diffraction peak appearing at diffraction angles of 8.4° to 9.0° at which a crystal lattice plane belongs to 200 and/or 020 planes is preferably 0.3 or more.