A power storage device , comprising: an electrode body having a flat shape and including a plurality of electrode sheets each having an electrode sheet body , and an electrode tab protruding from the electrode sheet body , in which the electrode tabs of the electrode sheets overlap one another in a tab thickness direction (TH) to form an electrode tab group ; a case in which the electrode body is accommodated; and an electrode terminal that is fixedly provided to the case , extends from inside to outside of the case , and is bonded to the electrode tab group in the case , wherein each of the electrode tabs includes at least one bent portion bent in the tab thickness direction (TH), and the electrode tabs constituting the electrode tab group each include a tab connection portion including a bonded portion that is located on an inside (WH1) in a tab width direction (WH) and bonded to the electrode terminal directly or through another or other electrode tabs , and the at least one bent portion includes a connection-side bent portion located close to the tab connection portion , characterized in that at least one of the electrode tabs constituting the electrode tab group has a shape in which a tab width (L2) of the connection-side bent portion is smaller than a tab width (L1) of the tab connection portion (L2<L1), wherein the at least one bent portion of each of the electrode tabs comprises a plurality of bent portions , the electrode tabs constituting the electrode tab group each further include a tab base portion , the plurality of bent portions include a base-side bent portion located closest to the tab base portion , and at least one of the electrode tabs constituting the electrode tab group has a shape in which a tab width (L4) of the base-side bent portion is smaller than a tab width (L3) of the tab base portion (L4<L3). an electrode body having a flat shape and including a plurality of electrode sheets each having an electrode sheet body , and an electrode tab protruding from the electrode sheet body , in which the electrode tabs of the electrode sheets overlap one another in a tab thickness direction (TH) to form an electrode tab group ; a case in which the electrode body is accommodated; and an electrode terminal that is fixedly provided to the case , extends from inside to outside of the case , and is bonded to the electrode tab group in the case , wherein each of the electrode tabs includes at least one bent portion bent in the tab thickness direction (TH), and the electrode tabs constituting the electrode tab group each include a tab connection portion including a bonded portion that is located on an inside (WH1) in a tab width direction (WH) and bonded to the electrode terminal directly or through another or other electrode tabs , and the at least one bent portion includes a connection-side bent portion located close to the tab connection portion , characterized in that at least one of the electrode tabs constituting the electrode tab group has a shape in which a tab width (L2) of the connection-side bent portion is smaller than a tab width (L1) of the tab connection portion (L2<L1), wherein the at least one bent portion of each of the electrode tabs comprises a plurality of bent portions , the electrode tabs constituting the electrode tab group each further include a tab base portion , the plurality of bent portions include a base-side bent portion located closest to the tab base portion , and at least one of the electrode tabs constituting the electrode tab group has a shape in which a tab width (L4) of the base-side bent portion is smaller than a tab width (L3) of the tab base portion (L4<L3). <EOS>