A blood purification apparatus comprising: a blood circuit that includes an arterial blood circuit and a venous blood circuit, and that is capable of extracorporeally circulating blood of a patient from a leading end of the arterial blood circuit to a leading end of the venous blood circuit; a blood purification means that is interposed between the arterial blood circuit and the venous blood circuit of the blood circuit, and that is capable of purifying blood that flows through the blood circuit; a blood pump disposed in the arterial blood circuit; a dialysate introduction line for introducing dialysate to the blood purification means, and a dialysate discharge line for discharging the dialysate from the blood purification means; a liquid delivery pump disposed in the dialysate introduction line; and a dialysate supply line that branches from a downstream side of the liquid delivery pump in the dialysate introduction line and is connected to the blood circuit for pre-dilution and/or post-dilution, and that is capable of supplying the dialysate of the dialysate introduction line to the blood circuit, wherein the blood purification apparatus includes a valve means that is capable of closing and opening the dialysate introduction line and the dialysate supply line in any manner, and a control unit configured to operate the valve means to allow blood purification to be performed selected from hemodialysis treatment in which the dialysate supply line is closed while the dialysate introduction line is opened, hemofiltration treatment in which the dialysate supply line is opened while the dialysate introduction line is closed, and hemodiafiltration treatment in which hemodialysis and hemofiltration are performed concurrently by alternately closing and opening the dialysate introduction line and the dialysate supply line wherein the valve means has a single movable unit that is disposed to straddle the dialysate introduction line and the dialysate supply line, and the movable unit is operable by an actuator to close one of the dialysate introduction line and the dialysate supply line and open the other as well as to close the other and open the one. a blood circuit that includes an arterial blood circuit and a venous blood circuit, and that is capable of extracorporeally circulating blood of a patient from a leading end of the arterial blood circuit to a leading end of the venous blood circuit; a blood purification means that is interposed between the arterial blood circuit and the venous blood circuit of the blood circuit, and that is capable of purifying blood that flows through the blood circuit; a blood pump disposed in the arterial blood circuit; a dialysate introduction line for introducing dialysate to the blood purification means, and a dialysate discharge line for discharging the dialysate from the blood purification means; a liquid delivery pump disposed in the dialysate introduction line; and a dialysate supply line that branches from a downstream side of the liquid delivery pump in the dialysate introduction line and is connected to the blood circuit for pre-dilution and/or post-dilution, and that is capable of supplying the dialysate of the dialysate introduction line to the blood circuit, wherein the blood purification apparatus includes a valve means that is capable of closing and opening the dialysate introduction line and the dialysate supply line in any manner, and a control unit configured to operate the valve means to allow blood purification to be performed selected from hemodialysis treatment in which the dialysate supply line is closed while the dialysate introduction line is opened, hemofiltration treatment in which the dialysate supply line is opened while the dialysate introduction line is closed, and hemodiafiltration treatment in which hemodialysis and hemofiltration are performed concurrently by alternately closing and opening the dialysate introduction line and the dialysate supply line wherein the valve means has a single movable unit that is disposed to straddle the dialysate introduction line and the dialysate supply line, and the movable unit is operable by an actuator to close one of the dialysate introduction line and the dialysate supply line and open the other as well as to close the other and open the one.