Method for producing hydrogen gas separation material

The invention provides a method for consistently producing a hydrogen gas separator with a good performance balance. The method includes the process for preparing a porous substrate and the process for forming a silica coat on the substrate by chemical vapor deposition in which a reaction is brought about between a silica source provided to one side of the substrate and an oxygen-containing gas supplied to the other side of the substrate. The vapor deposition process is carried out using as the silica source a silicon compound (a) with Si-Z-Si bonds (Z is O or N) in the molecule.