An electrophotographic photoreceptor includes: a conductive substrate; an undercoating layer that contains inorganic particles surface-treated with a surface treatment agent, and is provided in contact with an outer peripheral surface of the conductive substrate; and a photosensitive layer provided on the undercoating layer, wherein, with respect to the outer peripheral surface of the conductive substrate, a proportion of an area being in contact with the inorganic particles is from 82% to 91%.