A fuel cell humidifier comprising: a mid-case; a cap fastened to the mid-case; at least one cartridge disposed in the mid-case and accommodating a plurality of hollow fiber membranes; and a gasket assembly airtightly coupled to at least one end of a humidification module through mechanical assembly so that the cap is in fluid communication with only the hollow fiber membranes, the gasket assembly includes: a packing portion including a body member having a hole into which an end portion of the cartridge is inserted and two or more protruding members formed at one end of the body member, an edge portion formed at the other end of the body member and formed in a space formed by a groove formed in the end portion of the mid-case and the end portion of the cap, and a sealing portion formed to be in contact with the cartridge and the packing portion to prevent the fluid in the mid-case from flowing to the cap side, wherein the body member includes a lower body member formed to protrude the mid-case side and an upper body member formed in a flat surface shape toward the cap side, the cartridge includes the plurality of hollow fiber membranes and a potting portion for fixing the hollow fiber membranes to each other and ends of the hollow fiber membranes are fixed to the potting portion, wherein the two or more protruding members are in contact with the potting portion inserted into the hole to prevent a fluid in the mid-case from flowing to the cap side, wherein the sealing portion is formed so as to be in contact with the potting portion and the two or more protruding members at the same time, wherein the sealing portion is formed between two or more protruding members, and wherein the protruding members are in contact with the cartridge potting portion while pressing the cartridge potting portion to airtightly seal the space of the mid-case and the space by the cap, and thereby, areas in which the protruding members are formed implement further sealing areas. a mid-case; a cap fastened to the mid-case; at least one cartridge disposed in the mid-case and accommodating a plurality of hollow fiber membranes; and a gasket assembly airtightly coupled to at least one end of a humidification module through mechanical assembly so that the cap is in fluid communication with only the hollow fiber membranes, the gasket assembly includes: a packing portion including a body member having a hole into which an end portion of the cartridge is inserted and two or more protruding members formed at one end of the body member, an edge portion formed at the other end of the body member and formed in a space formed by a groove formed in the end portion of the mid-case and the end portion of the cap, and a sealing portion formed to be in contact with the cartridge and the packing portion to prevent the fluid in the mid-case from flowing to the cap side, wherein the body member includes a lower body member formed to protrude the mid-case side and an upper body member formed in a flat surface shape toward the cap side, the cartridge includes the plurality of hollow fiber membranes and a potting portion for fixing the hollow fiber membranes to each other and ends of the hollow fiber membranes are fixed to the potting portion, wherein the two or more protruding members are in contact with the potting portion inserted into the hole to prevent a fluid in the mid-case from flowing to the cap side, wherein the sealing portion is formed so as to be in contact with the potting portion and the two or more protruding members at the same time, wherein the sealing portion is formed between two or more protruding members, and wherein the protruding members are in contact with the cartridge potting portion while pressing the cartridge potting portion to airtightly seal the space of the mid-case and the space by the cap, and thereby, areas in which the protruding members are formed implement further sealing areas. a packing portion including a body member having a hole into which an end portion of the cartridge is inserted and two or more protruding members formed at one end of the body member, an edge portion formed at the other end of the body member and formed in a space formed by a groove formed in the end portion of the mid-case and the end portion of the cap, and a sealing portion formed to be in contact with the cartridge and the packing portion to prevent the fluid in the mid-case from flowing to the cap side, wherein the body member includes a lower body member formed to protrude the mid-case side and an upper body member formed in a flat surface shape toward the cap side, the cartridge includes the plurality of hollow fiber membranes and a potting portion for fixing the hollow fiber membranes to each other and ends of the hollow fiber membranes are fixed to the potting portion, wherein the two or more protruding members are in contact with the potting portion inserted into the hole to prevent a fluid in the mid-case from flowing to the cap side, wherein the sealing portion is formed so as to be in contact with the potting portion and the two or more protruding members at the same time, wherein the sealing portion is formed between two or more protruding members, and wherein the protruding members are in contact with the cartridge potting portion while pressing the cartridge potting portion to airtightly seal the space of the mid-case and the space by the cap, and thereby, areas in which the protruding members are formed implement further sealing areas.