A wastewater treatment system comprising: an acid fermentation tank configured to produce acid fermentation-treated water by treating raw wastewater with acidogenic bacteria; a first flow path connected to the acid fermentation tank and configured to transmit the acid fermentation-treated water; a methane fermentation tank positioned under the acid fermentation tank, connected to the first flow path, and configured to produce biogas and methane fermentation-treated water by treating the acid fermentation-treated water transmitted by the first flow path with methanogenic bacteria, and an upper portion of the methane fermentation tank including an opening that communicates with the acid fermentation tank; a second flow path connected to the methane fermentation tank and configured to transmit the methane fermentation-treated water; and a gas type liquid partition valve provided at the opening, including a gas storage portion configured to store a predetermined amount of the biogas and discharge the biogas exceeding the predetermined amount to the acid fermentation tank, and configured to block the opening with the biogas stored in the gas storage portion, wherein the gas type liquid partition valve includes a case member being disposed above the opening to face the opening and having an open bottom so as to define the gas storage portion; and a guide member defining a flow path through which the biogas can flow, including a lower end portion connected to the opening, and an outer diameter smaller than the inner diameter of the case member and the upper end portion of the guide member being higher than a lower portion of the case member, so that the guide member is disposed such that at least the upper end portion is accommodated inside the case member; wherein the gas type liquid partition valve is configured to allow the biogas produced in the methane fermentation tank to pass therethrough toward the acid fermentation tank while not allowing the raw wastewater or the acid fermentation-treated water in the acid fermentation tank to pass therethrough toward the methane fermentation tank. an acid fermentation tank configured to produce acid fermentation-treated water by treating raw wastewater with acidogenic bacteria; a first flow path connected to the acid fermentation tank and configured to transmit the acid fermentation-treated water; a methane fermentation tank positioned under the acid fermentation tank, connected to the first flow path, and configured to produce biogas and methane fermentation-treated water by treating the acid fermentation-treated water transmitted by the first flow path with methanogenic bacteria, and an upper portion of the methane fermentation tank including an opening that communicates with the acid fermentation tank; a second flow path connected to the methane fermentation tank and configured to transmit the methane fermentation-treated water; and a gas type liquid partition valve provided at the opening, including a gas storage portion configured to store a predetermined amount of the biogas and discharge the biogas exceeding the predetermined amount to the acid fermentation tank, and configured to block the opening with the biogas stored in the gas storage portion, wherein the gas type liquid partition valve includes a case member being disposed above the opening to face the opening and having an open bottom so as to define the gas storage portion; and a guide member defining a flow path through which the biogas can flow, including a lower end portion connected to the opening, and an outer diameter smaller than the inner diameter of the case member and the upper end portion of the guide member being higher than a lower portion of the case member, so that the guide member is disposed such that at least the upper end portion is accommodated inside the case member; wherein the gas type liquid partition valve is configured to allow the biogas produced in the methane fermentation tank to pass therethrough toward the acid fermentation tank while not allowing the raw wastewater or the acid fermentation-treated water in the acid fermentation tank to pass therethrough toward the methane fermentation tank.