A reaction container having one or two or more housing parts for reactions comprising: a narrow-mouthed piping part in which a reaction reagent or a portion thereof is housed or is housable; a wide-mouthed piping part that is communicated with the narrow-mouthed piping part and provided on an upper side of the narrow-mouthed piping part, and has an aperture that is wider than an aperture of said narrow-mouthed piping part; and a punchable film provided such that it partitions an interval between the wide-mouthed piping part and the narrow-mouthed piping part, and further a sealing lid that has a bottom surface, which has transparency, and that seals the reaction container by being mounted on the aperture of said wide-mouthed piping part of said reaction container, wherein said sealing lid has: a plug portion (251a, 252a, 253a) that is fittable to said wide-mouthed piping part, has the bottom surface at an end of the plug portion (251a, 252a, 253a) and is able to guide light from said narrow-mouthed piping part; and a pushing portion (251d, 252d, 253d) provided to the bottom surface that, in a case where the plug portion (251a, 252a, 253a) is fitted with the wide-mouthed piping part, pushes said film, which is insertable into the aperture of said narrow-mouthed piping part and is punched, into an inner wall of the narrow-mouthed piping part, and is also able to guide light from said narrow-mouthed piping part, wherein the pushing portion (251d, 252d, 253d) comprises a cylindrical wall extending vertically downward from the external bottom surface of the sealing lid and formed so as to circularly enclose a center portion through which the light guided by the sealing lid passes, at the external bottom surface. a narrow-mouthed piping part in which a reaction reagent or a portion thereof is housed or is housable; a wide-mouthed piping part that is communicated with the narrow-mouthed piping part and provided on an upper side of the narrow-mouthed piping part, and has an aperture that is wider than an aperture of said narrow-mouthed piping part; and a punchable film provided such that it partitions an interval between the wide-mouthed piping part and the narrow-mouthed piping part, and further a sealing lid that has a bottom surface, which has transparency, and that seals the reaction container by being mounted on the aperture of said wide-mouthed piping part of said reaction container, wherein said sealing lid has: a plug portion (251a, 252a, 253a) that is fittable to said wide-mouthed piping part, has the bottom surface at an end of the plug portion (251a, 252a, 253a) and is able to guide light from said narrow-mouthed piping part; and a pushing portion (251d, 252d, 253d) provided to the bottom surface that, in a case where the plug portion (251a, 252a, 253a) is fitted with the wide-mouthed piping part, pushes said film, which is insertable into the aperture of said narrow-mouthed piping part and is punched, into an inner wall of the narrow-mouthed piping part, and is also able to guide light from said narrow-mouthed piping part, wherein the pushing portion (251d, 252d, 253d) comprises a cylindrical wall extending vertically downward from the external bottom surface of the sealing lid and formed so as to circularly enclose a center portion through which the light guided by the sealing lid passes, at the external bottom surface. a plug portion (251a, 252a, 253a) that is fittable to said wide-mouthed piping part, has the bottom surface at an end of the plug portion (251a, 252a, 253a) and is able to guide light from said narrow-mouthed piping part; and a pushing portion (251d, 252d, 253d) provided to the bottom surface that, in a case where the plug portion (251a, 252a, 253a) is fitted with the wide-mouthed piping part, pushes said film, which is insertable into the aperture of said narrow-mouthed piping part and is punched, into an inner wall of the narrow-mouthed piping part, and is also able to guide light from said narrow-mouthed piping part, wherein the pushing portion (251d, 252d, 253d) comprises a cylindrical wall extending vertically downward from the external bottom surface of the sealing lid and formed so as to circularly enclose a center portion through which the light guided by the sealing lid passes, at the external bottom surface.