A manufacturing method of a liquid crystal optical device is provided including an alignment film forming step of forming an alignment film containing silicon oxide on a substrate, and a liquid crystal cell forming step of disposing a pair of substrates at least one of which the alignment film has been formed on, opposite to each other interposing a liquid crystal therebetween. In the alignment film forming step, the substrate surface is bombarded with a plasma beam generated by vacuum arc discharge using a cathode containing silicon, where the substrate is disposed on the course of the plasma beam obliquely with an angle. When the plasma beam bombards the substrate surface, plasma ions in the plasma beam have higher kinetic energy or higher flux density than plasma ions in a plasma beam which, if bombarding the substrate obliquely at the angle, form a film having a column structure.