The present invention provides a photosensitive letterpress printing original plate provided with a heat sensitive mask layer having high light blocking effect and durability yet prepared as a thin film. A photosensitive letterpress printing original plate including at least (A) a supporting member, (B) a photosensitive resin layer, and (C) a heat sensitive mask layer that are successively laminated, wherein the heat sensitive mask layer (C) contains carbon black and, as a dispersion binder therefor, a butyral resin as well as polyamide containing polar group selected from the group consisting of polyamide containing a tertiary amine group, polyamide containing a quaternary ammonium salt group, polyamide containing an ether group and polyamide containing a sulfonic group.