PURPOSE: To readily form complex ink flow channels and dented parts in the front, to uniform flying directions of ink particles and to improve printing qualities.

CONSTITUTION: In a process A, a photo mask 2 having formed an exposure pattern 2a and a shielding part 2b is arranged opposingly to an end face 1a of the photosensitive glass plate 1 and the photosensitive glass plate is exposed to light rays to form an exposure part for front dented part at the middle part of the front 1b of the photosensitive glass plate. In a process B, a photo mask 3 having formed an exposure pattern 3a and a shielding part 3b is arranged opposingly to the surface 1b of the photosensitive glass plate and the photosensitive glass plate is exposed to light rays to form exposure parts for channels on both the surface and the back. In a process C, both the exposure parts are heat-treated to form a crystal part 11 for front dented part and a crystal part 12 of channels. In a process D, the front except the crystal part 11 for the front dented part is covered with a masking material 6 and etched to form a dented part 4 in the front and channel parts 5 on both the surface and the back. The masking material 6 is removed to yield a flow channel substrate of ink jet head and vibration plates 7 are bonded to both faces of the surface and the back.