A layer-forming device that forms a thin layer on a substrate at the atomic level, the layer-forming device comprising: a feeding mechanism configured to feed the substrate during layer formation on the substrate; an injector unit including a plurality of injectors provided along a feeding passage of the substrate with gaps, and configured to supply a layer-forming gas toward the substrate to form, on the substrate being fed, a layer of a layer-forming component of the layer-forming gas; and a reactant supply unit configured to supply a reactant that reacts with the layer-forming component toward the substrate through the gaps, wherein a substrate opposing surface of each of the injectors, the surface facing the substrate includes a layer-forming gas supply slot configured to output the layer-forming gas, first gas exhaust slots provided on both sides of the layer-forming gas supply slot in a feeding direction of the substrate, and configured to suck an excess gas above the substrate, and inert gas supply slots provided on far sides of the respective first gas exhaust slots away from the layer-forming gas supply slot, in the feeding direction, and configured to output an inert gas; wherein the layer-forming gas supply slot, the first gas exhaust slots, and the inert gas supply slots form slit-like openings on the substrate opposing surface; characterized in that each of the injectors includes tubular continuous holes (60b, 60c, 62b, 62c, 64b, 64c) respectively connected with the layer-forming gas supply slot, the first gas exhaust slots, and the inert gas supply slots, inside injector members (70 to 80) that constitute each of the injectors, each of the continuous holes (60b, 60c, 62b, 62c, 64b, 64c) includes an opening (36, 38, 34) in the surface of the injector, and is connected with any one of a layer-forming gas supply pipe connected with a layer-forming gas source, an exhaust pipe connected with an exhaust device, and an inert gas supply pipe connected with an inert gas source, at the opening (36, 38, 34), and a part of each of the tubular continuous holes (62b, 62c, 64b, 64c) respectively connected with the first gas exhaust slots and the inert gas supply slots forms a ring shape inside the injector members (70 to 80). a feeding mechanism configured to feed the substrate during layer formation on the substrate; an injector unit including a plurality of injectors provided along a feeding passage of the substrate with gaps, and configured to supply a layer-forming gas toward the substrate to form, on the substrate being fed, a layer of a layer-forming component of the layer-forming gas; and a reactant supply unit configured to supply a reactant that reacts with the layer-forming component toward the substrate through the gaps, wherein a substrate opposing surface of each of the injectors, the surface facing the substrate includes a layer-forming gas supply slot configured to output the layer-forming gas, first gas exhaust slots provided on both sides of the layer-forming gas supply slot in a feeding direction of the substrate, and configured to suck an excess gas above the substrate, and inert gas supply slots provided on far sides of the respective first gas exhaust slots away from the layer-forming gas supply slot, in the feeding direction, and configured to output an inert gas; wherein the layer-forming gas supply slot, the first gas exhaust slots, and the inert gas supply slots form slit-like openings on the substrate opposing surface; characterized in that each of the injectors includes tubular continuous holes (60b, 60c, 62b, 62c, 64b, 64c) respectively connected with the layer-forming gas supply slot, the first gas exhaust slots, and the inert gas supply slots, inside injector members (70 to 80) that constitute each of the injectors, each of the continuous holes (60b, 60c, 62b, 62c, 64b, 64c) includes an opening (36, 38, 34) in the surface of the injector, and is connected with any one of a layer-forming gas supply pipe connected with a layer-forming gas source, an exhaust pipe connected with an exhaust device, and an inert gas supply pipe connected with an inert gas source, at the opening (36, 38, 34), and a part of each of the tubular continuous holes (62b, 62c, 64b, 64c) respectively connected with the first gas exhaust slots and the inert gas supply slots forms a ring shape inside the injector members (70 to 80).