A method of manufacturing a cartridge type hollow fiber membrane module comprising: a housing; a hollow-fiber membrane bundle having a plurality of hollow fiber membranes; a first potting part that bonds the hollow fiber membranes at at least one end of the bundle of the plurality of hollow fiber membranes such that the hollow fiber membranes are open; and a sealing material that seals the first potting part to the housing liquid-tightly or in case a cylindrical case is contained in the housing, a sealing material seals the first potting part to the housing liquid-tightly, wherein the first potting part comprises an inner potting part and an outer potting part, wherein the inner potting part and the outer potting part are both formed of a potting material, wherein the sealing material is in contact with the outer potting part, and wherein both the inner potting part and the outer potting part are formed in a sealing direction of the sealing material, wherein in the case where the sealing material seals the first potting part to the housing liquid-tightly, the first potting part has a proportion of length P (%) satisfies Expression below, wherein P (%) represents the proportion of the length of the outer potting part in the sealing direction in the length of the first potting part in the sealing direction: P ≤ 16 the method comprising the steps of: (a) forming an inner potting part included in the first potting part; and (b) forming an outer potting part included in the first potting part, the step (a) comprising: (a-1) an inner potting material disposing step in which a potting material for forming the inner potting part is filled between the hollow fiber membranes; and (a-2) a curing step in which the potting material in (a-1) is cured, the step (b) comprising: (b-1) an outer potting material disposing step in which a potting material for forming the outer potting part is disposed such that after the curing step (a-2), the outer potting part comes into contact with the sealing material and both the inner potting part and the outer potting part are formed in the sealing direction of the sealing material; and (b-2) a curing step in which the potting material in (b-1) is cured and shrunk. a housing; a hollow-fiber membrane bundle having a plurality of hollow fiber membranes; a first potting part that bonds the hollow fiber membranes at at least one end of the bundle of the plurality of hollow fiber membranes such that the hollow fiber membranes are open; and a sealing material that seals the first potting part to the housing liquid-tightly or in case a cylindrical case is contained in the housing, a sealing material seals the first potting part to the housing liquid-tightly, wherein the first potting part comprises an inner potting part and an outer potting part, wherein the inner potting part and the outer potting part are both formed of a potting material, wherein the sealing material is in contact with the outer potting part, and wherein both the inner potting part and the outer potting part are formed in a sealing direction of the sealing material, wherein in the case where the sealing material seals the first potting part to the housing liquid-tightly, the first potting part has a proportion of length P (%) satisfies Expression below, wherein P (%) represents the proportion of the length of the outer potting part in the sealing direction in the length of the first potting part in the sealing direction: P ≤ 16 the method comprising the steps of: (a) forming an inner potting part included in the first potting part; and (b) forming an outer potting part included in the first potting part, (a) forming an inner potting part included in the first potting part; and (b) forming an outer potting part included in the first potting part, the step (a) comprising: (a-1) an inner potting material disposing step in which a potting material for forming the inner potting part is filled between the hollow fiber membranes; and (a-2) a curing step in which the potting material in (a-1) is cured, (a-1) an inner potting material disposing step in which a potting material for forming the inner potting part is filled between the hollow fiber membranes; and (a-2) a curing step in which the potting material in (a-1) is cured, the step (b) comprising: (b-1) an outer potting material disposing step in which a potting material for forming the outer potting part is disposed such that after the curing step (a-2), the outer potting part comes into contact with the sealing material and both the inner potting part and the outer potting part are formed in the sealing direction of the sealing material; and (b-2) a curing step in which the potting material in (b-1) is cured and shrunk. (b-1) an outer potting material disposing step in which a potting material for forming the outer potting part is disposed such that after the curing step (a-2), the outer potting part comes into contact with the sealing material and both the inner potting part and the outer potting part are formed in the sealing direction of the sealing material; and (b-2) a curing step in which the potting material in (b-1) is cured and shrunk.