A beverage container (1,100) comprising: a container main body that contains a beverage; an inner lid portion (3,30) that covers the container main body; a spout portion (8,18) which is formed on the inner lid portion (3,30) and through which the beverage is discharged; a spout blocking portion (3h,30h) that blocks the spout portion (8,18); an outer lid portion (5,50) disposed so as to be able to engage with and disengage from the inner lid portion (3,30); a ventilation portion (10,110) that allows air to flow between the inside and the outside of the container main body; and a vent blocking portion (12h,120) formed on the outer lid portion (5,50) or the inner lid portion (3,30) to block the ventilation portion (10,110) when the outer lid portion (5,50) is placed to close the inner lid portion (3,30), wherein a cancellation operation portion (12c,122) which cancels engagement between the outer lid portion (5,50) and the inner lid portion (3,30) is formed, and the beverage container (1,100) further comprises a ventilation adjusting protruding portion (12i,121) which projects from the vent blocking portion (12h,120) and which is configured to allow the ventilation portion (10,110) to perform a ventilation operation on the basis of a cancelation operation by the cancellation operation portion, characterised in that the ventilation portion (10,110) has a slit portion (10a,110a) formed of an elastic member, and the ventilation adjusting protruding portion (12i,121) is configured to be able to enlarge the slit portion (10a,110a) by moving a position of the ventilation adjusting protruding portion (12i,121) in association with the operation of the cancellation operation portion (12c,122), wherein the ventilation portion (10,110) has a cylindrical portion, and the slit portion (10a,110a) and the ventilation adjusting protruding portion (12i,121) are arranged in the cylindrical portion. a container main body that contains a beverage; an inner lid portion (3,30) that covers the container main body; a spout portion (8,18) which is formed on the inner lid portion (3,30) and through which the beverage is discharged; a spout blocking portion (3h,30h) that blocks the spout portion (8,18); an outer lid portion (5,50) disposed so as to be able to engage with and disengage from the inner lid portion (3,30); a ventilation portion (10,110) that allows air to flow between the inside and the outside of the container main body; and a vent blocking portion (12h,120) formed on the outer lid portion (5,50) or the inner lid portion (3,30) to block the ventilation portion (10,110) when the outer lid portion (5,50) is placed to close the inner lid portion (3,30), wherein a cancellation operation portion (12c,122) which cancels engagement between the outer lid portion (5,50) and the inner lid portion (3,30) is formed, and the beverage container (1,100) further comprises a ventilation adjusting protruding portion (12i,121) which projects from the vent blocking portion (12h,120) and which is configured to allow the ventilation portion (10,110) to perform a ventilation operation on the basis of a cancelation operation by the cancellation operation portion, characterised in that the ventilation portion (10,110) has a slit portion (10a,110a) formed of an elastic member, and the ventilation adjusting protruding portion (12i,121) is configured to be able to enlarge the slit portion (10a,110a) by moving a position of the ventilation adjusting protruding portion (12i,121) in association with the operation of the cancellation operation portion (12c,122), wherein the ventilation portion (10,110) has a cylindrical portion, and the slit portion (10a,110a) and the ventilation adjusting protruding portion (12i,121) are arranged in the cylindrical portion.