A blood purification apparatus comprising: a blood circuit through which blood of a patient is allowed to extracorporeally circulate; a blood purification device that purifies the blood flowing in the blood circuit; a storage device capable of storing a predetermined amount of dialysate that is necessary for blood purification treatment; a dialysate circulation line through which the dialysate is allowed to circulate by introducing the dialysate in the storage device into the blood purification device and draining waste liquid from the blood purification device into the storage device ; and a dialysate purification device that purifies the dialysate in the dialysate circulation line, wherein a treatment state in which the dialysate circulating through the dialysate circulation line is allowed to be introduced into the blood purification device without flowing through the dialysate purification device and a purification state in which the dialysate in the dialysate circulation line is allowed to be purified by the dialysate purification device are taken switchably, and wherein the purification state is taken if a predetermined condition is satisfied after a start of the treatment state, characterized in that the blood purification apparatus further comprises a waste-matter-concentration measurement device (S) capable of measuring a concentration of waste matter in the dialysate circulating through the dialysate circulation line, wherein the predetermined condition is defined as reaching of the concentration of waste matter measured by the waste-matter-concentration measurement device (S) to a predetermined concentration after the start of the treatment state. a blood circuit through which blood of a patient is allowed to extracorporeally circulate; a blood purification device that purifies the blood flowing in the blood circuit; a storage device capable of storing a predetermined amount of dialysate that is necessary for blood purification treatment; a dialysate circulation line through which the dialysate is allowed to circulate by introducing the dialysate in the storage device into the blood purification device and draining waste liquid from the blood purification device into the storage device ; and a dialysate purification device that purifies the dialysate in the dialysate circulation line, wherein a treatment state in which the dialysate circulating through the dialysate circulation line is allowed to be introduced into the blood purification device without flowing through the dialysate purification device and a purification state in which the dialysate in the dialysate circulation line is allowed to be purified by the dialysate purification device are taken switchably, and wherein the purification state is taken if a predetermined condition is satisfied after a start of the treatment state, characterized in that the blood purification apparatus further comprises a waste-matter-concentration measurement device (S) capable of measuring a concentration of waste matter in the dialysate circulating through the dialysate circulation line, wherein the predetermined condition is defined as reaching of the concentration of waste matter measured by the waste-matter-concentration measurement device (S) to a predetermined concentration after the start of the treatment state. <EOS>