A molten material treatment apparatus comprising: a container having an upper portion, on which a molten material injection part is disposed, and a bottom part in which a hole is formed; a gas injection part attached to the bottom part between the molten material injection part and the hole; a chamber part formed on the upper portion of the container so as to face the gas injection part and having an inside open downward; a plurality of vertical members disposed so as to cross a plurality of positions of a rotary flow region formed between the chamber part and the bottom part; and a dam member formed between the gas injection part and the hole along a boundary of the rotary flow region so as to cross a lower portion of the container, wherein the gas injection part is attached to the bottom part so as to be positioned between at least any two of the vertical members, wherein the chamber part comprises: a first wall body; and a second wall body, wherein the first wall body is positioned between the molten material injection part and the gas injection part, the second wall body is positioned between the gas injection part and the hole, and the plurality of vertical members are positioned between the first wall body and the second wall body, wherein each of the first wall body and the second wall body has a lower end extending to a height immersible into the molten material injected into the container, wherein the second wall body is spaced from and disposed above the dam member, wherein the dam member has a lower end contacting the bottom part and an upper end formed in a height separable downward from the second wall body. a container having an upper portion, on which a molten material injection part is disposed, and a bottom part in which a hole is formed; a gas injection part attached to the bottom part between the molten material injection part and the hole; a chamber part formed on the upper portion of the container so as to face the gas injection part and having an inside open downward; a plurality of vertical members disposed so as to cross a plurality of positions of a rotary flow region formed between the chamber part and the bottom part; and a dam member formed between the gas injection part and the hole along a boundary of the rotary flow region so as to cross a lower portion of the container, wherein the gas injection part is attached to the bottom part so as to be positioned between at least any two of the vertical members, wherein the chamber part comprises: a first wall body; and a second wall body, wherein the first wall body is positioned between the molten material injection part and the gas injection part, the second wall body is positioned between the gas injection part and the hole, and the plurality of vertical members are positioned between the first wall body and the second wall body, wherein each of the first wall body and the second wall body has a lower end extending to a height immersible into the molten material injected into the container, wherein the second wall body is spaced from and disposed above the dam member, wherein the dam member has a lower end contacting the bottom part and an upper end formed in a height separable downward from the second wall body. a first wall body; and a second wall body, wherein the first wall body is positioned between the molten material injection part and the gas injection part, the second wall body is positioned between the gas injection part and the hole, and the plurality of vertical members are positioned between the first wall body and the second wall body, wherein each of the first wall body and the second wall body has a lower end extending to a height immersible into the molten material injected into the container, wherein the second wall body is spaced from and disposed above the dam member, wherein the dam member has a lower end contacting the bottom part and an upper end formed in a height separable downward from the second wall body. <EOS>