A method for manufacturing an electricity storage device including an electricity storage member in which positive electrode foils (11a, 11b) and negative electrode foils (12a, 12b) are alternately stacked with separator foils interposed therebetween, comprising: a positive electrode folding; a negative electrode folding; and an initial arranging in which a positive electrode material foil and a negative electrode material foil are arranged with the separator foils interposed therebetween such that an opening of the folded positive electrode material foil faces an opening of the folded negative electrode material foil; characterized by a positioning in which the positive electrode material foil and the negative electrode material foil are positioned by relatively moving the folded positive electrode material foil and the folded negative electrode material foil closer to each other so as to insert one end of a second material foil (11b; 12b) among the positive and negative electrode material foils (11a, 11b; 12a, 12b) from the opening of a first material foil (11a; 12a) among the positive and negative electrode material foils (11a, 11b; 12a, 12b) toward a bottom of a valley of the first material foil (11a; 12a), and in which the one end of the second material foil (11b; 12b) is restrained with the bottom of the valley of the first material foil (11a; 12a), wherein in the positive electrode folding the positive electrode material foil having a length equal to a sum of lengths of two of the positive electrode foils (11a, 11b) is folded in a middle; and in the negative electrode folding the negative electrode material foil having a length equal to a sum of lengths of two of the negative electrode foils (12a, 12b) is folded in a middle. a positive electrode folding; a negative electrode folding; and an initial arranging in which a positive electrode material foil and a negative electrode material foil are arranged with the separator foils interposed therebetween such that an opening of the folded positive electrode material foil faces an opening of the folded negative electrode material foil; characterized by a positioning in which the positive electrode material foil and the negative electrode material foil are positioned by relatively moving the folded positive electrode material foil and the folded negative electrode material foil closer to each other so as to insert one end of a second material foil (11b; 12b) among the positive and negative electrode material foils (11a, 11b; 12a, 12b) from the opening of a first material foil (11a; 12a) among the positive and negative electrode material foils (11a, 11b; 12a, 12b) toward a bottom of a valley of the first material foil (11a; 12a), and in which the one end of the second material foil (11b; 12b) is restrained with the bottom of the valley of the first material foil (11a; 12a), wherein in the positive electrode folding the positive electrode material foil having a length equal to a sum of lengths of two of the positive electrode foils (11a, 11b) is folded in a middle; and in the negative electrode folding the negative electrode material foil having a length equal to a sum of lengths of two of the negative electrode foils (12a, 12b) is folded in a middle.