A secondary battery, comprising: a top cover plate; an electrode terminal (300, 400) disposed on the top cover plate; two electrode assemblies arranged side by side in a thickness direction of the secondary battery, wherein each of the two electrode assemblies comprises a main body and a plurality of conductive portions extending from the main body, the plurality of conductive portions is stacked and forms a tab (720, 730), and the main body is formed by winding a first electrode plate, a second electrode plate, and a separator disposed between the first electrode plate and the second electrode plate; a connecting piece (500, 600) for connecting the tab (720, 730) to the electrode terminal (300, 400); and a supporting piece; wherein the tab (720, 730) extends from a side of the main body viewed in the thickness direction of the secondary battery, and the tab (720, 730) is bent with respect to a height direction of the secondary battery and connected to the connecting piece (500, 600), the tab (720, 730) comprises a connecting portion for main body connected to the main body, an extending portion connected to the connecting piece (500, 600), and a bending portion connected between the connecting portion for main body and the extending portion, the extending portion extends along the thickness direction of the secondary battery, and the bending portion is bent with respect to the extending portion, characterized in that, the supporting piece is disposed between the main body and the extending portion, wherein the main body has a first side and a second side, the tab (720, 730) is provided at the first side, none of the tab (720, 730) is provided at the second side, the bending portion and the connecting portion for main body are located at the first side, and the second sides of two main bodies of the two electrode assemblies are adjacent to each other, the supporting piece comprises a supporting portion and a guiding portion, the guiding portion is connected to an end of the supporting portion and bent with respect to the supporting portion, the supporting portion is attached to the extending portion, and the guiding portion is attached to the bending portion. a top cover plate; an electrode terminal (300, 400) disposed on the top cover plate; two electrode assemblies arranged side by side in a thickness direction of the secondary battery, wherein each of the two electrode assemblies comprises a main body and a plurality of conductive portions extending from the main body, the plurality of conductive portions is stacked and forms a tab (720, 730), and the main body is formed by winding a first electrode plate, a second electrode plate, and a separator disposed between the first electrode plate and the second electrode plate; a connecting piece (500, 600) for connecting the tab (720, 730) to the electrode terminal (300, 400); and a supporting piece; wherein the tab (720, 730) extends from a side of the main body viewed in the thickness direction of the secondary battery, and the tab (720, 730) is bent with respect to a height direction of the secondary battery and connected to the connecting piece (500, 600), the tab (720, 730) comprises a connecting portion for main body connected to the main body, an extending portion connected to the connecting piece (500, 600), and a bending portion connected between the connecting portion for main body and the extending portion, the extending portion extends along the thickness direction of the secondary battery, and the bending portion is bent with respect to the extending portion, characterized in that, the supporting piece is disposed between the main body and the extending portion, wherein the main body has a first side and a second side, the tab (720, 730) is provided at the first side, none of the tab (720, 730) is provided at the second side, the bending portion and the connecting portion for main body are located at the first side, and the second sides of two main bodies of the two electrode assemblies are adjacent to each other, the supporting piece comprises a supporting portion and a guiding portion, the guiding portion is connected to an end of the supporting portion and bent with respect to the supporting portion, the supporting portion is attached to the extending portion, and the guiding portion is attached to the bending portion.