Disclosed is a method of manufacturing a liquid jet head, which enables a passage-forming substrate to be easily handled, thus realizing good formation of pressure generating chambers and an improvement in manufacturing efficiency. The method includes the steps of: forming a vibration plate and piezoelectric elements on one surface of the passage-forming substrate; thermally adhering a reinforcing substrate for reinforcing the rigidity of the passage-forming substrate, onto the passage-forming substrate; processing the passage-forming substrate to have a predetermined thickness; depositing an insulation film on other surface of the passage-forming substrate at lower temperature than that for adhering the passage-forming substrate and the reinforcing substrate, and patterning the insulation film into a predetermined shape; and etching the passage-forming substrate using the patterned insulation film as a mask to form the pressure generating chambers. Thus, handling of the passage-forming substrate becomes easy, and the pressure generating chambers can be formed with high precision.