To provide an ink jet record head having a nozzle shape capable of promptly curbing meniscus vibrations occurring on refilling and stably performing discharge. A second discharge port portion 10 has a form in which, with a lower side of a square on a bubbling chamber 8 side, angles on an upper side of the square are curved respectively on any cross section vertical to a principal surface of an element substrate on which heaters 1 are formed and going through the center of a discharge port 4, and these curves are shaped as arcs of circles of a radius R inscribed in the angles on the upper side of the square respectively.