A battery, comprising: an electrode group comprising a positive electrode comprising an active material-containing layer and a positive electrode current collector, a negative electrode comprising an active material-containing layer and a negative electrode current collector, a first separator provided between the positive and negative electrodes, a positive electrode current collector tab that projects from one end portion of the electrode group, and a negative electrode current collector tab that projects from the other end portion of the electrode group in a direction opposite to the positive electrode current collector tab projecting direction;a case comprising a first film and a second film and having a case portion (5, 6) and first and second edge portions provided at a circumference of the case portion (5, 6), each of the first and second edge portions (5a, 6b) comprising a heat sealed part and a non-sealed part; the first edge portion and the second edge portion being bonded through heat sealing, a positive electrode lead electrically connected to the positive electrode current collector tab such that an end portion extends outwardly through the edge portion (5a, 6a) of the case; and a negative electrode lead electrically connected to the negative electrode current collector tab such that an end portion extends outwardly through the edge portion (5a, 6a) of the case, characterized by the electrode group being spirally wound in a flat shape so that a first portion of the electrode group corresponding to the positive and negative electrodes and the first separator is located between the positive electrode current collector tab and the negative electrode current collector tab, wherein the electrode group is housed in the case portion (5, 6) while an end portion of at least one of the positive electrode current collector tab and the negative electrode current collector tab is directly nipped from the non-sealed part of the edge portion of the case. an electrode group comprising a positive electrode comprising an active material-containing layer and a positive electrode current collector, a negative electrode comprising an active material-containing layer and a negative electrode current collector, a first separator provided between the positive and negative electrodes, a positive electrode current collector tab that projects from one end portion of the electrode group, and a negative electrode current collector tab that projects from the other end portion of the electrode group in a direction opposite to the positive electrode current collector tab projecting direction;a case comprising a first film and a second film and having a case portion (5, 6) and first and second edge portions provided at a circumference of the case portion (5, 6), each of the first and second edge portions (5a, 6b) comprising a heat sealed part and a non-sealed part; the first edge portion and the second edge portion being bonded through heat sealing, a positive electrode comprising an active material-containing layer and a positive electrode current collector, a negative electrode comprising an active material-containing layer and a negative electrode current collector, a first separator provided between the positive and negative electrodes, a positive electrode current collector tab that projects from one end portion of the electrode group, and a negative electrode current collector tab that projects from the other end portion of the electrode group in a direction opposite to the positive electrode current collector tab projecting direction;a case comprising a first film and a second film and having a case portion (5, 6) and first and second edge portions provided at a circumference of the case portion (5, 6), each of the first and second edge portions (5a, 6b) comprising a heat sealed part and a non-sealed part; the first edge portion and the second edge portion being bonded through heat sealing, a positive electrode lead electrically connected to the positive electrode current collector tab such that an end portion extends outwardly through the edge portion (5a, 6a) of the case; and a negative electrode lead electrically connected to the negative electrode current collector tab such that an end portion extends outwardly through the edge portion (5a, 6a) of the case,