An electric device having a curved structure (601, 602, 604, 605) formed at at least one position of an outside thereof, wherein at least one secondary battery having an external appearance corresponding to a shape of the curved structure (601, 602, 604, 605) is mounted at the position of the electric device at which the curved structure is formed, and wherein the secondary battery is a battery cell (300, 400, 500) having an electrode assembly comprising a cathode, an anode, and a separator disposed between the cathode and the anode mounted in a battery case, or a battery pack having the battery cell mounted in a pack case, wherein the battery cell (300, 400, 500) is configured to have a rectangular parallelepiped structure comprising six faces, and comprises a top face (361, 461, 561) and a bottom face, the top face and the bottom face being opposite to each other, four side faces (363, 364, 365, 463, 464, 465, 563, 564, 565) tangent to the top face and the bottom face, four side edges (382, 482, 582) forming interfaces between the respective side faces, four upper edges (372, 373, 472, 473, 572, 573) forming interfaces between the top face and the respective side faces, and four lower edges forming interfaces between the bottom face and the respective side faces, and a round corner (R3, R4, R5) having the shape of the curved structure (601, 602, 604, 605) of the electric device is formed at at least one selected from among the upper edges (372, 373, 472, 473, 572, 573), the lower edges, and the side edges (382, 482, 582) of the battery cell (300, 400, 500), characterized in that the battery cell (300, 400) has electrode terminals (340, 341, 440, 441) formed at one side face (363, 463) thereof, and the round corner (R3, R4) is formed at one upper edge (372, 373, 472, 473) and at least one side edge (382, 482) of the battery cell which are not tangent to one side face at which the electrode terminals are formed such that the top face and at least one side face of the battery cell are connected to each other in a continuously curved form; or the battery cell has electrode terminals (540, 541) formed at one side face thereof, and the round corner is formed at one upper edge (572, 573), one lower edge, and at least one side edge of the battery cell which are not tangent to one side face at which the electrode terminals are formed such that the top face, the bottom face, and at least one side face of the battery cell are connected to each other in a continuously curved form. at least one secondary battery having an external appearance corresponding to a shape of the curved structure (601, 602, 604, 605) is mounted at the position of the electric device at which the curved structure is formed, and wherein the secondary battery is a battery cell (300, 400, 500) having an electrode assembly comprising a cathode, an anode, and a separator disposed between the cathode and the anode mounted in a battery case, or a battery pack having the battery cell mounted in a pack case, wherein the battery cell (300, 400, 500) is configured to have a rectangular parallelepiped structure comprising six faces, and comprises a top face (361, 461, 561) and a bottom face, the top face and the bottom face being opposite to each other, four side faces (363, 364, 365, 463, 464, 465, 563, 564, 565) tangent to the top face and the bottom face, four side edges (382, 482, 582) forming interfaces between the respective side faces, four upper edges (372, 373, 472, 473, 572, 573) forming interfaces between the top face and the respective side faces, and four lower edges forming interfaces between the bottom face and the respective side faces, and a round corner (R3, R4, R5) having the shape of the curved structure (601, 602, 604, 605) of the electric device is formed at at least one selected from among the upper edges (372, 373, 472, 473, 572, 573), the lower edges, and the side edges (382, 482, 582) of the battery cell (300, 400, 500), characterized in that the battery cell (300, 400) has electrode terminals (340, 341, 440, 441) formed at one side face (363, 463) thereof, and the round corner (R3, R4) is formed at one upper edge (372, 373, 472, 473) and at least one side edge (382, 482) of the battery cell which are not tangent to one side face at which the electrode terminals are formed such that the top face and at least one side face of the battery cell are connected to each other in a continuously curved form; or the battery cell has electrode terminals (540, 541) formed at one side face thereof, and the round corner is formed at one upper edge (572, 573), one lower edge, and at least one side edge of the battery cell which are not tangent to one side face at which the electrode terminals are formed such that the top face, the bottom face, and at least one side face of the battery cell are connected to each other in a continuously curved form.