According to one embodiment, a first substrate has a pair of thermosensitive films, a heater film, and a passage protective film having corrosion resistance in a passage forming region on a first main surface, and has a metal sealing film having corrosion resistance in a region other than the passage forming region. A second substrate has a groove formed in the passage forming region on a second main surface and a side wall forming portion separating other regions other than the passage forming region from the groove and protruding beyond the other regions. A fixing member fixes the first substrate to the second substrate. The side wall forming portion of the second substrate is compression bonded so that the side wall forming portion is located on the metal sealing film on the first substrate.