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