A pouch type secondary battery has a safety vent which prevents explosion and fire by removing a sealing mechanism of a pouch casing when the internal temperature increases due to overcharging, overdischarging or over-heating, and which exhausts internal gas before explosion and fire of the battery when the internal gas pressure excessively increases due to overcharging, overdischarging or internal short-circuit. The pouch type secondary battery includes an electrode assembly having positive and negative electrode plates with a separator interposed therebetween, and positive and negative electrode terminals extending from the positive and negative electrode plates, respectively, a pouch casing having a space in which the electrode assembly is housed to be sealed, a seal portion provided at the periphery of the space, and at least one of the positive and negative electrode terminals exposed to the seal portion, and at least one opening member disposed at the seal portion and made of a resin material having a lower melting point than a melting point of the seal portion of the pouch casing.