To ensure parallelism between the surface of a substrate arranged with energy generating elements and the surface of a reference plate for securing the substrate.

A recess having a depth Δd narrower than the width of an energy generating element substrate 1 is made in a reference plate 6 and coated with an adhesive 7. Coating height of the adhesive 7 is set higher than the depth Δd of the recess. The energy generating element substrate 1 is positioned above the reference plate 6 and then placed on the reference plate 6. Subsequently, the energy generating element substrate 1 is pressed against the reference plate 6 in order to collapse the adhesive 7 and a part of the energy generating element substrate 1 is abutted against the reference plate 6. When the adhesive 7 is hardened under that state, shrinkage takes place to generate a force for drawing the adhesive 7 inward. Consequently, the energy generating element substrate 1 adheres further to the bonding face of the reference plate 6.