A method for manufacturing a battery cell including an electrode assembly and electrolyte provided in a battery case made of a laminate sheet having a resin layer and a metal layer, comprising: (a) mounting the electrode assembly in the battery case and sealing the periphery of the battery case except for one end part thereof through thermal fusion; (b) introducing the electrolyte through the unsealed end part and sealing said end part via thermal fusion; (c) charging-discharging the battery cell to activate the same; (d) transferring gas generated during activation and excess electrolyte to said end part of the battery case of the battery cell by centrifugal force; (e) removing the gas and excess electrolyte from said end part, wherein operation (e) includes: puncturing a part in said end part to form a through-hole communicating with the battery case; and pulling top and bottom faces of the battery case in the opposite direction to each other at the part in said end part to open the same while applying vacuum pressure thereto, to remove excess electrolyte as well as the gas generated during activation, wherein the top and bottom faces of the battery case are pulled in opposite directions by a suction device while applying vacuum pressure thereto, wherein the suction device comprises a first suction pad contacting the top face of the battery case and a second suction pad contacting the bottom face of the same, and wherein each of the first suction pad and the second suction pad has a structure comprising an adhesion part contacting the outer side of the battery case and a hollow part that is connected to the adhesion part, communicates with a through-hole formed at the part of the battery case and applies vacuum pressure; (f) sealing the inner side of said end part through thermal fusion and then cutting off the outer part. (a) mounting the electrode assembly in the battery case and sealing the periphery of the battery case except for one end part thereof through thermal fusion; (b) introducing the electrolyte through the unsealed end part and sealing said end part via thermal fusion; (c) charging-discharging the battery cell to activate the same; (d) transferring gas generated during activation and excess electrolyte to said end part of the battery case of the battery cell by centrifugal force; (e) removing the gas and excess electrolyte from said end part, wherein operation (e) includes: puncturing a part in said end part to form a through-hole communicating with the battery case; and pulling top and bottom faces of the battery case in the opposite direction to each other at the part in said end part to open the same while applying vacuum pressure thereto, to remove excess electrolyte as well as the gas generated during activation, wherein the top and bottom faces of the battery case are pulled in opposite directions by a suction device while applying vacuum pressure thereto, wherein the suction device comprises a first suction pad contacting the top face of the battery case and a second suction pad contacting the bottom face of the same, and wherein each of the first suction pad and the second suction pad has a structure comprising an adhesion part contacting the outer side of the battery case and a hollow part that is connected to the adhesion part, communicates with a through-hole formed at the part of the battery case and applies vacuum pressure; (f) sealing the inner side of said end part through thermal fusion and then cutting off the outer part.