A method of manufacturing an ink jet head, which includes a discharge port for discharging an ink droplet, an ink flow path communicated with the discharge port, and an energy generating element for discharging the ink droplet from the discharge port, includes providing a photodegradable resin layer on a substrate having the energy generating element, forming a structure which becomes the ink flow path by exposing and developing the photodegradable resin layer, coating the substrate having the structure which becomes the ink flow path with a negative type photosensitive resin layer, forming the ink discharge port in the negative type photosensitive resin layer, and forming the ink flow path communicated with the discharge port by removing the structure which becomes the ink flow path. The photodegradable resin layer includes a binary acrylic copolymer composition, which contains a unit obtained from (meta)acrylic ester as a main component and further contains a unit obtained from (meta)acrylic acid. The composition contains the (meta)acrylic acid unit at a proportion of 5 to 30 weight %, and a weight average molecular weight of the composition ranges from 50000 to 300000.