A secondary battery in which an electrode assembly and an electrolyte are inserted and injected into a pouch, and an edge of the pouch is sealed to form a sealing portion, the secondary battery comprising: a valve fixed to the sealing portion so that one end thereof faces the inside of the pouch, and the other end thereof faces the outside of the pouch, wherein the valve comprises: a body forming a passage having opened one end facing the inside of the pouch and provided with a chamber connected to the passage, wherein a discharge hole communicating with the outside is formed in the chamber; a gate seated on a hook protrusion forming a boundary between the passage and the chamber to open or close the passage; and a spring mounted to apply elastic force in a direction in which the gate is closed, wherein the gate is configured to be opened to discharge the gas through the discharge hole when a gas is generated inside the pouch so that a pressure of the gas overcomes the elastic force of the spring, and wherein an auxiliary discharge hole is formed so that when the gate slides inside the chamber, air within the chamber is discharged, wherein the auxiliary discharge hole is formed at an opposite side of the discharge hole with the gate therebetween. a valve fixed to the sealing portion so that one end thereof faces the inside of the pouch, and the other end thereof faces the outside of the pouch, wherein the valve comprises: a body forming a passage having opened one end facing the inside of the pouch and provided with a chamber connected to the passage, wherein a discharge hole communicating with the outside is formed in the chamber; a gate seated on a hook protrusion forming a boundary between the passage and the chamber to open or close the passage; and a spring mounted to apply elastic force in a direction in which the gate is closed, wherein the gate is configured to be opened to discharge the gas through the discharge hole when a gas is generated inside the pouch so that a pressure of the gas overcomes the elastic force of the spring, and wherein an auxiliary discharge hole is formed so that when the gate slides inside the chamber, air within the chamber is discharged, wherein the auxiliary discharge hole is formed at an opposite side of the discharge hole with the gate therebetween. a body forming a passage having opened one end facing the inside of the pouch and provided with a chamber connected to the passage, wherein a discharge hole communicating with the outside is formed in the chamber; a gate seated on a hook protrusion forming a boundary between the passage and the chamber to open or close the passage; and a spring mounted to apply elastic force in a direction in which the gate is closed, wherein the gate is configured to be opened to discharge the gas through the discharge hole when a gas is generated inside the pouch so that a pressure of the gas overcomes the elastic force of the spring, and wherein an auxiliary discharge hole is formed so that when the gate slides inside the chamber, air within the chamber is discharged, wherein the auxiliary discharge hole is formed at an opposite side of the discharge hole with the gate therebetween.