PROBLEM TO BE SOLVED: To provide a hollow fiber membrane type medical device including header shape capable of simultaneously materializing reduction of a priming volume and improvement of distributivity of blood.SOLUTION: This hollow fiber membrane type medical device 1 includes a cylindrical container 3, a hollow fiber membrane bundle 5, potting resin parts 7, headers 10, and ports 9. It is assumed that a cross section when having cut an inner space A of the header 10 along a direction orthogonal to the axis CS of the cylindrical container 3 is a cross section of the header, the header 10 has a height h wherein the volume per cross section of the header 10 is 1.0×10or below of the volume of hollow fiber membranes 4 and a pressure loss applied to the header 10 to a pressure loss applied to the hollow fiber membranes 4 is 1.5-7.0%, and a side surface S2 sectionalizing the inner space A of the header 10 is an inclined surface inclined toward outward from an edge part of a counter surface S1 when viewing in a cross section along the direction of the axis and is inclined to the end faces 4c of the hollow fiber membranes 4 by 15-70°.
