A blood reservoir being capable of reducing damage to blood stored therein. The blood reservoir has a housing in the form of a box, and filtering and defoaming devices provided in the housing, i.e., a device for filtering and defoaming on blood suctioned from a surgical field (outside a heart), a device for filtering and defoaming on blood vented from the interior of the heart, and a device for filtering and defoaming on blood drawn off from a large vein. The vented blood flowing into the blood reservoir passes through a vented blood filtering member to be introduced into a blood storage space without contacting an antifoaming agent and foreign substances filtered off from the suctioned blood.
