A liquid-mixing infusor comprising: a liquid mixing infusor main body defining a chamber which is formed in a cylindrical shape and defines an axial direction; a branching portion formed above said chamber and equipped with a connectable or interruptible flow path to an inside of said chamber ; a pair of branch tubes extending outwards from said chamber and respectively having flow paths connected to the inside of said chamber ; a valve installed inside said chamber , the valve rotatable in a periaxial direction of said chamber ; and a rotary portion extending outside of said chamber from said valve and having an operation portion rotatable in the periaxial direction of said chamber on an outside of said chamber to rotate said valve ; said operation portion is rotatable to rotate said valve between a first blocking state in which connection between both of said pair of branch tubes and said chamber is blocked; a second blocking state in which connection between one of said pair of branch tubes and said chamber is blocked, and a connecting state in which both of said pair of branch tubes and said branching portion are connected through said chamber , characterized in that said branching portion is arranged about a reference vertical axis, the vertical axis extending between the branch tubes of said pair of branch tubes , said branching portion vertically displaced relative to said pair of branch tubes , and wherein said valve includes a vertical wall generally extending along the reference vertical axis and above said pair of branch tubes , the vertical wall dimensioned to prevent back flow of fluid between the branch tubes of said pair of branch tubes when said operation portion is in said connecting state. a liquid mixing infusor main body defining a chamber which is formed in a cylindrical shape and defines an axial direction; a branching portion formed above said chamber and equipped with a connectable or interruptible flow path to an inside of said chamber ; a pair of branch tubes extending outwards from said chamber and respectively having flow paths connected to the inside of said chamber ; a valve installed inside said chamber , the valve rotatable in a periaxial direction of said chamber ; and a rotary portion extending outside of said chamber from said valve and having an operation portion rotatable in the periaxial direction of said chamber on an outside of said chamber to rotate said valve ; said operation portion is rotatable to rotate said valve between a first blocking state in which connection between both of said pair of branch tubes and said chamber is blocked; a second blocking state in which connection between one of said pair of branch tubes and said chamber is blocked, and a connecting state in which both of said pair of branch tubes and said branching portion are connected through said chamber , characterized in that said branching portion is arranged about a reference vertical axis, the vertical axis extending between the branch tubes of said pair of branch tubes , said branching portion vertically displaced relative to said pair of branch tubes , and wherein said valve includes a vertical wall generally extending along the reference vertical axis and above said pair of branch tubes , the vertical wall dimensioned to prevent back flow of fluid between the branch tubes of said pair of branch tubes when said operation portion is in said connecting state. <EOS>