Provided is a method of manufacturing a liquid injection head, the method including: forming, on a substrate, a negative photosensitive resin layer having a first surface on a side opposite to the substrate and a second surface on the substrate side; carrying out first exposure of the negative photosensitive resin layer; carrying out second exposure of the negative photosensitive resin layer; and forming the ejection orifice by carrying out development after the first exposure and the second exposure in which each of the first surface and the second surface has a portion in which a part of the unexposed portion in the first exposure and a part of the unexposed portion in the second exposure overlap and a portion in which a part of the unexposed portion in the first exposure and a part of the unexposed portion in the second exposure do not overlap.