Provided is a method of manufacturing a liquid ejection head, including: forming, on a substrate, a flow path mold pattern that becomes a mold of a liquid flow path; forming a negative photosensitive resin layer on the flow path mold pattern; subjecting the negative photosensitive resin layer to exposure processing with use of a reduction projection exposing apparatus and a mask pattern having an ejection orifice mask shape for forming ejection orifices; and subjecting the negative photosensitive resin layer obtained after the exposure processing to development processing to form the ejection orifices, in which the ejection orifices are formed by correcting, by the ejection orifice mask shape, an inclination of an ejection angle due to an off-axis telecentricity caused by the reduction projection exposing apparatus so as to be close to a direction perpendicular to a surface of the substrate.