To obtain an electrophotographic photoreceptor having superior potential stability and improved sensitivity characteristics by incorporating a specified bisazo pigment and a specified acetal resin.

The electrophotographic photoreceptor has a photosensitive layer on the electrically conductive substrate and the photosensitive layer contains a bisazo pigment represented by formula I and an acetal resin having structural units represented by formula II. In the formula, Cp is the residue of a coupler having a phenolic hydroxyl group, Ar1 is arylene which may have a substituent, Ar2 and Ar3 are each phenyl which may have a substituent and (m) is an integer of 0-2. The photosensitive layer is particularly preferably a function separated photosensitive layer formed by laminating an electric charge transferring layer contg. an electric charge transferring material on an electric charge generating layer contg. the bisazo pigment and the acetal resin in a weight ratio of 10:1 to 1:10, preferably 5:1 to 1:2.