A humidifier for a fuel cell, the humidifier comprising: a humidifying module configured to humidify gas supplied from outside using moisture in off-gas discharged from a fuel cell stack; and caps coupled respectively to opposite ends of the humidifying module, wherein the humidifying module comprises: a mid-case open at opposite ends thereof; a plurality of hollow fiber membranes disposed in the mid-case; a fixing layer in which ends of the hollow fiber membranes are potted; and a composite gasket having a groove into which the end of the mid-case is inserted, the composite gasket comprises: an inner body based on the groove, the inner body being located inside the mid-case; an outer body based on the groove, the outer body being located outside the mid-case; and a connecting body located between the inner body and the outer body, the humidifier characterized in that: the connecting body is formed of a first material having hardness of 30 to 60 Shore A, and at least a portion of the inner body is adhered to the fixing layer and is formed of a second material different from the first material, the second material having higher adhesive force with respect to the fixing layer than the first material. a humidifying module configured to humidify gas supplied from outside using moisture in off-gas discharged from a fuel cell stack; and caps coupled respectively to opposite ends of the humidifying module, wherein the humidifying module comprises: a mid-case open at opposite ends thereof; a plurality of hollow fiber membranes disposed in the mid-case; a fixing layer in which ends of the hollow fiber membranes are potted; and a composite gasket having a groove into which the end of the mid-case is inserted, the composite gasket comprises: an inner body based on the groove, the inner body being located inside the mid-case; an outer body based on the groove, the outer body being located outside the mid-case; and a connecting body located between the inner body and the outer body, the humidifier characterized in that: the connecting body is formed of a first material having hardness of 30 to 60 Shore A, and at least a portion of the inner body is adhered to the fixing layer and is formed of a second material different from the first material, the second material having higher adhesive force with respect to the fixing layer than the first material. a mid-case open at opposite ends thereof; a plurality of hollow fiber membranes disposed in the mid-case; a fixing layer in which ends of the hollow fiber membranes are potted; and a composite gasket having a groove into which the end of the mid-case is inserted, the composite gasket comprises: an inner body based on the groove, the inner body being located inside the mid-case; an outer body based on the groove, the outer body being located outside the mid-case; and a connecting body located between the inner body and the outer body, the humidifier characterized in that: the connecting body is formed of a first material having hardness of 30 to 60 Shore A, and at least a portion of the inner body is adhered to the fixing layer and is formed of a second material different from the first material, the second material having higher adhesive force with respect to the fixing layer than the first material. an inner body based on the groove, the inner body being located inside the mid-case; an outer body based on the groove, the outer body being located outside the mid-case; and a connecting body located between the inner body and the outer body, the humidifier characterized in that: the connecting body is formed of a first material having hardness of 30 to 60 Shore A, and at least a portion of the inner body is adhered to the fixing layer and is formed of a second material different from the first material, the second material having higher adhesive force with respect to the fixing layer than the first material. the connecting body is formed of a first material having hardness of 30 to 60 Shore A, and at least a portion of the inner body is adhered to the fixing layer and is formed of a second material different from the first material, the second material having higher adhesive force with respect to the fixing layer than the first material.