A medical instrument comprising: a first laminate having a plurality of first hollow fiber membrane layers which each have a plurality of first hollow fiber membranes, and wherein said first laminate forms a shape of a cylindrical body as a whole, and a second laminate having a plurality of second hollow fiber membrane layers which each have a plurality of second hollow fiber membranes, said second hollow fiber membranes being disposed at the outer circumferential side of the first hollow fiber membranes, and wherein said second laminate forms a shape of a cylindrical body as a whole, wherein in the first laminate, each of the first hollow fiber membranes sequentially passes through a starting point which is set at one site of one end of the cylindrical body, a midpoint which is set at one site of the other end of the cylindrical body such that the midpoint is placed in the almost same position as the starting point in the circumferential direction of the cylindrical body, and an endpoint which is set at one site which is in the same position as the starting point or is in a position deviating from the starting point around the central axis, is wound at least once along the circumferential direction of the cylindrical body in the outward path heading for the midpoint from the starting point, and is wound by the same number of turns in the same direction as in the case of the outward path in the homeward path heading for the endpoint from the midpoint; wherein in the second laminate, each of the second hollow fiber membranes sequentially passes through a starting point which is set at one site of one end of the cylindrical body, a midpoint which is set at one site of the other end of the cylindrical body such that the midpoint is located in a position opposite to the starting point across the central axis of the cylindrical body, and an endpoint which is set at one site which is in the same position as the starting point or is in a position deviating from the starting point around the central axis, reaches the midpoint from the starting point at the shortest distance while being wound along the circumferential direction of the cylindrical body by half a circumference (semicircumference) in the outward path heading for the midpoint from the starting point, and reaches the endpoint from the midpoint at the shortest distance while being wound along the circumferential direction of the cylindrical body by the same number of turns in the same direction as in the case of the outward path in the homeward path heading for the endpoint from the midpoint. a first laminate having a plurality of first hollow fiber membrane layers which each have a plurality of first hollow fiber membranes, and wherein said first laminate forms a shape of a cylindrical body as a whole, and a second laminate having a plurality of second hollow fiber membrane layers which each have a plurality of second hollow fiber membranes, said second hollow fiber membranes being disposed at the outer circumferential side of the first hollow fiber membranes, and wherein said second laminate forms a shape of a cylindrical body as a whole, wherein in the first laminate, each of the first hollow fiber membranes sequentially passes through a starting point which is set at one site of one end of the cylindrical body, a midpoint which is set at one site of the other end of the cylindrical body such that the midpoint is placed in the almost same position as the starting point in the circumferential direction of the cylindrical body, and an endpoint which is set at one site which is in the same position as the starting point or is in a position deviating from the starting point around the central axis, is wound at least once along the circumferential direction of the cylindrical body in the outward path heading for the midpoint from the starting point, and is wound by the same number of turns in the same direction as in the case of the outward path in the homeward path heading for the endpoint from the midpoint; wherein in the second laminate, each of the second hollow fiber membranes sequentially passes through a starting point which is set at one site of one end of the cylindrical body, a midpoint which is set at one site of the other end of the cylindrical body such that the midpoint is located in a position opposite to the starting point across the central axis of the cylindrical body, and an endpoint which is set at one site which is in the same position as the starting point or is in a position deviating from the starting point around the central axis, reaches the midpoint from the starting point at the shortest distance while being wound along the circumferential direction of the cylindrical body by half a circumference (semicircumference) in the outward path heading for the midpoint from the starting point, and reaches the endpoint from the midpoint at the shortest distance while being wound along the circumferential direction of the cylindrical body by the same number of turns in the same direction as in the case of the outward path in the homeward path heading for the endpoint from the midpoint.