Abstract: Provided are: a resin composition for the formation of an optical waveguide, which shows low transmission loss and high heat stability and enables to form a waveguide pattern at high shape accuracy and at low cost; an optical waveguide; a method of forming an optical waveguide; and an optical element using the method. A photosensitive resin composition is used, which includes a polyamic acid represented by a general formula (I) or a polyamic acid ester (A), a compound (B) having an epoxy group, and a compound (C) which generates an acid by being exposed to light.