A molten metal furnace comprising: an outer wall in an outer peripheral portion; and a molten metal storage part holding molten metal, wherein a plurality of lining material layers are arranged on an inner wall of the molten metal furnace forming the molten metal storage part, among the plurality of lining material layers, a first lining layer constituting a surface in contact with the molten metal is made of a refractory material, and a sealing material is provided on at least one boundary between the first lining layer and the outer wall, wherein the sealing material has a sheet shape with a thickness of 2 to 10 mm, and is provided in a single layer or a plurality of laminated layers, wherein the sealing material is a sheet material obtained by weaving at least one of ceramic fibers and biosoluble ceramic fibers and at least one of glass fibers and stainless steel fibers, and wherein the biosoluble ceramic fiber is selected from fibers classified in Category 0 (exempt substances) in the "EU Directive 97/69/EC" regulation, such a fiber needs to be a fiber whose safety is verified based on Nota Q "criteria for biosoluble fibers" for any of the following four animal experiments, or a fiber in which a numerical value obtained by subtracting a value twice the standard deviation from the length weighted geometric average diameter exceeds 6 μm, based on Nota R "criteria for non-inhalable fibers", In a bioretention test by short-term inhalation, fibers longer than 20 μm have a load half-life of less than 10 days In a bioretention test by short-term intratracheal injection, fibers longer than 20 μm have a load half-life of less than 40 days No evidence of excessive carcinogenicity by intraperitoneal administration test, No relevant pathogenic changes or neoplastic changes in long-term inhalation test. an outer wall in an outer peripheral portion; and a molten metal storage part holding molten metal, wherein a plurality of lining material layers are arranged on an inner wall of the molten metal furnace forming the molten metal storage part, among the plurality of lining material layers, a first lining layer constituting a surface in contact with the molten metal is made of a refractory material, and a sealing material is provided on at least one boundary between the first lining layer and the outer wall, wherein the sealing material has a sheet shape with a thickness of 2 to 10 mm, and is provided in a single layer or a plurality of laminated layers, wherein the sealing material is a sheet material obtained by weaving at least one of ceramic fibers and biosoluble ceramic fibers and at least one of glass fibers and stainless steel fibers, and wherein the biosoluble ceramic fiber is selected from fibers classified in Category 0 (exempt substances) in the "EU Directive 97/69/EC" regulation, such a fiber needs to be a fiber whose safety is verified based on Nota Q "criteria for biosoluble fibers" for any of the following four animal experiments, or a fiber in which a numerical value obtained by subtracting a value twice the standard deviation from the length weighted geometric average diameter exceeds 6 μm, based on Nota R "criteria for non-inhalable fibers", In a bioretention test by short-term inhalation, fibers longer than 20 μm have a load half-life of less than 10 days In a bioretention test by short-term intratracheal injection, fibers longer than 20 μm have a load half-life of less than 40 days No evidence of excessive carcinogenicity by intraperitoneal administration test, No relevant pathogenic changes or neoplastic changes in long-term inhalation test. In a bioretention test by short-term inhalation, fibers longer than 20 μm have a load half-life of less than 10 days In a bioretention test by short-term intratracheal injection, fibers longer than 20 μm have a load half-life of less than 40 days No evidence of excessive carcinogenicity by intraperitoneal administration test, No relevant pathogenic changes or neoplastic changes in long-term inhalation test.