A degassing device, for discharging a gas generated in a secondary battery to the outside, the degassing device comprising: a piercing unit comprising a piercing body, configured to be disposed on a first surface of the secondary battery to seal one side of the first surface of the secondary battery, and a piercing member for piercing the one side of the first surface of the secondary battery, which is sealed by the piercing body to form an opening hole; and a gas discharge unit comprising a gas discharge body configured to be disposed on a second surface of the secondary battery to seal one side of the second surface of the secondary battery, in which the opening hole is formed, and a gas discharge member for discharging the gas within the secondary battery to the outside through the opening hole that is sealed by the gas discharge body, wherein the piercing member is configured to form the opening hole passing from the one side of the first surface to and through the one side of the second surface of the secondary battery, wherein the degassing device further comprises a sealing unit for sealing a surface of the secondary battery in which the opening hole is formed, wherein the sealing unit comprises first and second heating members (131, 132) for pressing both side surfaces of the secondary battery, in which the opening hole is formed, and simultaneously applying heat to both the sides surfaces of the secondary battery to seal the opening hole, wherein the first and second heating members (131, 132) press the secondary battery and simultaneously apply heat to the secondary battery to seal the opening hole, and wherein the first heating member comprises a first insertion surface inserted into a first insertion groove formed in one surface of the piercing body in a shape that surrounds the first sealing part and a first sealing surface for sealing the one side of the first surface of the secondary battery, in which the opening hole is formed, wherein the first sealing surface has a size less than that of the first insertion surface, and the second heating member comprises a second insertion surface inserted into a second insertion groove formed in one surface of the gas discharge body in a shape that surrounds the second sealing part and a second sealing surface for sealing the one side of the second surface of the secondary battery, in which the opening hole is formed, wherein the second sealing surface has a size less than that of the second insertion surface. a piercing unit comprising a piercing body, configured to be disposed on a first surface of the secondary battery to seal one side of the first surface of the secondary battery, and a piercing member for piercing the one side of the first surface of the secondary battery, which is sealed by the piercing body to form an opening hole; and a gas discharge unit comprising a gas discharge body configured to be disposed on a second surface of the secondary battery to seal one side of the second surface of the secondary battery, in which the opening hole is formed, and a gas discharge member for discharging the gas within the secondary battery to the outside through the opening hole that is sealed by the gas discharge body, wherein the piercing member is configured to form the opening hole passing from the one side of the first surface to and through the one side of the second surface of the secondary battery, wherein the degassing device further comprises a sealing unit for sealing a surface of the secondary battery in which the opening hole is formed, wherein the sealing unit comprises first and second heating members (131, 132) for pressing both side surfaces of the secondary battery, in which the opening hole is formed, and simultaneously applying heat to both the sides surfaces of the secondary battery to seal the opening hole, wherein the first and second heating members (131, 132) press the secondary battery and simultaneously apply heat to the secondary battery to seal the opening hole, and wherein the first heating member comprises a first insertion surface inserted into a first insertion groove formed in one surface of the piercing body in a shape that surrounds the first sealing part and a first sealing surface for sealing the one side of the first surface of the secondary battery, in which the opening hole is formed, wherein the first sealing surface has a size less than that of the first insertion surface, and the second heating member comprises a second insertion surface inserted into a second insertion groove formed in one surface of the gas discharge body in a shape that surrounds the second sealing part and a second sealing surface for sealing the one side of the second surface of the secondary battery, in which the opening hole is formed, wherein the second sealing surface has a size less than that of the second insertion surface.