To obtain a flexographic original printing plate capable of forming a mask with laser beam and with non-development.

The photosensitive original printing plate is formed by laminating (A) a photopolymerizable layer containing at least an elastomer based binder, an ethylenic unsaturated compound and a photopolymerization initiator having photosensitivity to non-infrared active ray, (B) an infrared light-heat converting layer having a material capable of converting the (B-a) infrared ray to the heat and a mask forming layer having a heat sensitive layer, which becomes substantially opaque by the (B-a) heat, and if necessary, (C) a cover film in this order.