Method for manufacturing electricity storage device

An electricity storage member (10) in an electricity storage device (1) is manufactured by a step of folding a positive electrode material foil (30) and folding a negative electrode material foil (40), a step of arranging the positive and negative electrode material foils (30), (40) with a separator foil (13) interposed therebetween, and a step of positioning the positive and negative electrode material foils by relatively moving the positive and negative electrode material foils (30), (40) toward each other so as to insert one end of a second material foil among the positive and negative electrode material foils into a bottom of a valley of the first material foil, and restraining the one end of the second material foil with the bottom of the valley of the first material foil.