There is provided a blood purification apparatus with which the efficiency of dialysate purification can be improved and the reduction in the amount of electrolytes contained in dialysate and necessary for treatment can be suppressed. The blood purification apparatus includes a storage device 6 capable of storing a predetermined amount of dialysate that is necessary for blood purification treatment, a dialysate circulation line (a dialysate introduction line L1 and a dialysate drain line L2) through which the dialysate is allowed to circulate by introducing the dialysate in the storage device 6 into the dialyzer 1 and draining waste liquid from the dialyzer 1 into the storage device 6, and the dialysate purification device 7 that purifies the dialysate in the dialysate circulation line. A treatment state in which the dialysate is allowed to be introduced into the dialyzer 1 without flowing through the dialysate purification device 7 and a purification state in which the dialysate is allowed to be purified by the dialysate purification device 7 are taken switchably. The purification state is taken if a predetermined condition is satisfied after the start of the treatment state.
