A method for manufacturing a secondary battery, the method comprising: a forming step of pressing a pouch sheet by using a press die so that left and right accommodation grooves (121, 122), which are bilaterally symmetrical to each other and are opened upward, and a bridge connecting the left and right accommodation grooves (121, 122) to each other are formed in the pouch sheet to form a pouch sheet so that an electrode assembly is accommodated; and a folding step of seating the electrode assembly on one of the left and right accommodation grooves (121, 122) to fold the electrode assembly so that the left and right accommodation grooves (121, 122) face each other, wherein, in the forming step, the pouch sheet is formed so that the bridge protrudes upward with respect to bottom surfaces (128, 129) of the left and right accommodation grooves, and a curved portion having a rounded shape is formed on an upper end of the bridge, characterized in that in the forming step, when a length between a portion, which contacts a lower edge of the electrode assembly adjacent to the bridge in the pouch sheet, and the bridge is d1, a length between a portion, which contacts an upper edge of the electrode assembly adjacent to the bridge in the pouch sheet, and the bridge is d2, a length of the bridge is d3, and a height of the electrode assembly seated on the pouch sheet is h, the pouch sheet is formed to satisfy following conditional expression: h ≤ d1+d2+d3, in the forming step, the pouch sheet is formed so that the bottom surfaces (128, 129) of the left and right accommodation grooves (121, 122) are inclined to be bilaterally symmetrical to each other, and the bottom surfaces (128, 129) of the left and right accommodation grooves (121, 122) have inclinations gradually decreasing in a direction that is away from the bridge. a forming step of pressing a pouch sheet by using a press die so that left and right accommodation grooves (121, 122), which are bilaterally symmetrical to each other and are opened upward, and a bridge connecting the left and right accommodation grooves (121, 122) to each other are formed in the pouch sheet to form a pouch sheet so that an electrode assembly is accommodated; and a folding step of seating the electrode assembly on one of the left and right accommodation grooves (121, 122) to fold the electrode assembly so that the left and right accommodation grooves (121, 122) face each other, wherein, in the forming step, the pouch sheet is formed so that the bridge protrudes upward with respect to bottom surfaces (128, 129) of the left and right accommodation grooves, and a curved portion having a rounded shape is formed on an upper end of the bridge, characterized in that in the forming step, when a length between a portion, which contacts a lower edge of the electrode assembly adjacent to the bridge in the pouch sheet, and the bridge is d1, a length between a portion, which contacts an upper edge of the electrode assembly adjacent to the bridge in the pouch sheet, and the bridge is d2, a length of the bridge is d3, and a height of the electrode assembly seated on the pouch sheet is h, the pouch sheet is formed to satisfy following conditional expression: h ≤ d1+d2+d3, in the forming step, the pouch sheet is formed so that the bottom surfaces (128, 129) of the left and right accommodation grooves (121, 122) are inclined to be bilaterally symmetrical to each other, and the bottom surfaces (128, 129) of the left and right accommodation grooves (121, 122) have inclinations gradually decreasing in a direction that is away from the bridge.