A method of manufacturing a liquid discharge head in which a device substrate having an energy generating element and a supply port and a supporting member having a supply passage are bonded with each other an adhesive agent includes: a first step of applying the adhesive agent to an end surface of a wall; a second step of flattening out the adhesive agent on the end surface of the wall of the supply port in the height direction intersecting the end surface by moving the end surface of the wall of the supply port and the end surface of the wall of the supply passage toward each other; and a third step of moving the ridge line of the wall of the supply port in a direction along the end surface of the wall of the supply port.