A blood processing device involving a small amount of remaining blood, comprising a hollow fiber module fixed to a housing by a partition wall with an end thereof opened and a blood port mounted to the opened end face and provided with a blood inlet, characterized in that an inclination &thetas of the inner wall of the blood inlet provided to the blood port with respect to the center axis of the blood port is not larger than 1.5 DEG and a relation 0.08D&leh&le0.13D holds, where Q is a point of intersection between a virtual line passing the end (P) of the blood port inner face and crossing the partition wall at right angles and a virtual extension line of the blood port ceiling face, h a distance between the point Q and the partition wall, and D a diameter of the end of the blood port inner face, the blood processing device being suitably used for blood purification, hemodialysis and ultrafiltration.
