A fermenter comprising: a fermentation container having a fermentation space in which a beverage is fermented and a first gas passage communicating with the fermentation space; and a fermentation lid opening and closing the fermentation container and having a second gas passage, wherein the fermentation container comprises: a fermentation tank having an opening opened and closed by the fermentation lid; and a beverage making pack having the fermentation space and the first gas passage, and being inserted into the fermentation tank through the opening; wherein a gas chamber is provided between the beverage making pack and the fermentation lid, and communicates with each of the first gas passage and the second gas passage, and the first gas passage, the gas chamber and the second gas passage constitute a gas passage through which the gas generated in the fermentation space can be discharged to the outside of the fermenter, wherein the gas chamber has a sectional area greater than that of each of the first gas passage and the second gas passage, wherein a container-side hollow part protruding upward is defined in the beverage making pack, and a lid-side hollow part protruding downward is defined in the fermentation lid, wherein a grasp part protruding upward is disposed on the beverage making pack, a portion of the grasp part is disposed inside the container-side hollow part, wherein a protrusion protruding downward is disposed on the fermentation lid, at least a portion of the protrusion is disposed inside the lid-side hollow part, wherein an inner space of the grasp part is provided in the gas chamber or communicates with the gas chamber, wherein, when the fermentation lid closes the opening, a buffer space is defined between the beverage making pack and the fermentation lid, and the buffer space is disposed outside the grasp part and spaced apart from the gas chamber, a space between the lid-side hollow part and the protrusion and a space between the container-side hollow part and the grasp part form the buffer space together with each other. a fermentation container having a fermentation space in which a beverage is fermented and a first gas passage communicating with the fermentation space; and a fermentation lid opening and closing the fermentation container and having a second gas passage, wherein the fermentation container comprises: a fermentation tank having an opening opened and closed by the fermentation lid; and a beverage making pack having the fermentation space and the first gas passage, and being inserted into the fermentation tank through the opening; a fermentation tank having an opening opened and closed by the fermentation lid; and a beverage making pack having the fermentation space and the first gas passage, and being inserted into the fermentation tank through the opening; wherein a gas chamber is provided between the beverage making pack and the fermentation lid, and communicates with each of the first gas passage and the second gas passage, and the first gas passage, the gas chamber and the second gas passage constitute a gas passage through which the gas generated in the fermentation space can be discharged to the outside of the fermenter, wherein the gas chamber has a sectional area greater than that of each of the first gas passage and the second gas passage, wherein a container-side hollow part protruding upward is defined in the beverage making pack, and a lid-side hollow part protruding downward is defined in the fermentation lid, wherein a grasp part protruding upward is disposed on the beverage making pack, a portion of the grasp part is disposed inside the container-side hollow part, wherein a protrusion protruding downward is disposed on the fermentation lid, at least a portion of the protrusion is disposed inside the lid-side hollow part, wherein an inner space of the grasp part is provided in the gas chamber or communicates with the gas chamber, wherein, when the fermentation lid closes the opening, a buffer space is defined between the beverage making pack and the fermentation lid, and the buffer space is disposed outside the grasp part and spaced apart from the gas chamber, a space between the lid-side hollow part and the protrusion and a space between the container-side hollow part and the grasp part form the buffer space together with each other.