A power storage device, comprising: an electrode body (20A, 20B) having a flat shape and including a plurality of electrode sheets (21A, 21B, 25A, 25B) each having an electrode sheet body (31A, 31B, 41A, 41B), and an electrode tab (32A, 32B, 42A, 42B) protruding from the electrode sheet body (31A, 31B, 41A, 41B), in which the electrode tabs (32A, 32B, 42A, 42B) of the electrode sheets (21A, 21B, 25A, 25B) overlap one another in a tab thickness direction to form an electrode tab group (38A, 38B, 48A, 48B); a case in which the electrode body (20A, 20B) is accommodated; and an electrode terminal (50, 60) that is fixedly provided to the case, extends from inside to outside of the case, and is bonded to the electrode tab group (38A, 38B, 48A, 48B) in the case, wherein each of the electrode tabs (32A, 32B, 42A, 42B) includes at least one bent portion (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B) bent in the tab thickness direction, and the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) each include a tab connection portion (33A, 33B, 43A, 43B) including a bonded portion (33Ay,33By, 43Ay, 43By) that is located on an inside in a tab width direction and bonded to the electrode terminal (50, 60) directly or through another or other electrode tabs (32A, 32B, 42A, 42B), and the at least one bent portion (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B) includes a connection-side bent portion (34A, 34B, 44A, 44B) located close to the tab connection portion (33A, 33B, 43A, 43B), characterized in that at least one of the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) has a shape in which a tab width of the connection-side bent portion (34A, 34B, 44A, 44B) is smaller than a tab width of the tab connection portion (33A, 33B, 43A, 43B) (L2<L1), wherein the at least one bent portion of each of the electrode tabs (32A, 32B, 42A, 42B) comprises a plurality of bent portions (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B), the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) each further include a tab base portion (36A, 36B, 46A, 46B), the plurality of bent portions (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B) include a base-side bent portion (35A, 35B, 45A, 45B) located closest to the tab base portion (36A, 36B, 46A, 46B), and at least one of the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) has a shape in which a tab width of the base-side bent portion (35A, 35B, 45A, 45B) is smaller than a tab width of the tab base portion (36A, 36B, 46A, 46B) (L4<L3). an electrode body (20A, 20B) having a flat shape and including a plurality of electrode sheets (21A, 21B, 25A, 25B) each having an electrode sheet body (31A, 31B, 41A, 41B), and an electrode tab (32A, 32B, 42A, 42B) protruding from the electrode sheet body (31A, 31B, 41A, 41B), in which the electrode tabs (32A, 32B, 42A, 42B) of the electrode sheets (21A, 21B, 25A, 25B) overlap one another in a tab thickness direction to form an electrode tab group (38A, 38B, 48A, 48B); a case in which the electrode body (20A, 20B) is accommodated; and an electrode terminal (50, 60) that is fixedly provided to the case, extends from inside to outside of the case, and is bonded to the electrode tab group (38A, 38B, 48A, 48B) in the case, wherein each of the electrode tabs (32A, 32B, 42A, 42B) includes at least one bent portion (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B) bent in the tab thickness direction, and the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) each include a tab connection portion (33A, 33B, 43A, 43B) including a bonded portion (33Ay,33By, 43Ay, 43By) that is located on an inside in a tab width direction and bonded to the electrode terminal (50, 60) directly or through another or other electrode tabs (32A, 32B, 42A, 42B), and the at least one bent portion (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B) includes a connection-side bent portion (34A, 34B, 44A, 44B) located close to the tab connection portion (33A, 33B, 43A, 43B), characterized in that at least one of the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) has a shape in which a tab width of the connection-side bent portion (34A, 34B, 44A, 44B) is smaller than a tab width of the tab connection portion (33A, 33B, 43A, 43B) (L2<L1), wherein the at least one bent portion of each of the electrode tabs (32A, 32B, 42A, 42B) comprises a plurality of bent portions (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B), the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) each further include a tab base portion (36A, 36B, 46A, 46B), the plurality of bent portions (34A, 34B, 35A, 35B, 44A, 44B, 45A, 45B) include a base-side bent portion (35A, 35B, 45A, 45B) located closest to the tab base portion (36A, 36B, 46A, 46B), and at least one of the electrode tabs (32A, 32B, 42A, 42B) constituting the electrode tab group (38A, 38B, 48A, 48B) has a shape in which a tab width of the base-side bent portion (35A, 35B, 45A, 45B) is smaller than a tab width of the tab base portion (36A, 36B, 46A, 46B) (L4<L3).