To prevent an inside plug from being left and an opening part of a bottle main body when a cap is removed for taking-out liquid from a liquid bottle and eliminate a troublesome work in which the inside plug is removed from the bottle main body.

This liquid bottle is comprised of a bottle main body; an inside plug fixed to an opening part of the bottle main body; and a cap threadably fitted to the opening part and pressed from above against the inside plug and engaged with it. The inside plug is comprised of an inside plug main body fitted along an inner circumferential surface of the opening part; and a flange part extending from an upper end of the inside plug main body in a circumferential direction and extending onto an upper end surface of the opening part. The cap is comprised of a top plate part; and a barrel part integral with the top plate part and for holding the flange part of the inside plug between the top plate part and the upper end surface of the opening part as the cap is threadably engaged with the opening. Further, either the barrel part or the inner portion of the top plate is provided with an engaging part for always engaging and housing a part of the flange part of the inside plug or the inside plug main body.