A charging method for charging N electricity storage elements (C 1,...,C N), N being equal to or larger than 3, by connecting the electricity storage elements (C 1,...,C N) electrically by a connector, when a series degree of a two-terminal circuit is defined as follows: the series degree is a number of unit circuits (U 1,..., Us) connected in series, each of the unit circuits (U 1,..., Us) being composed of a single electricity storage element (C 1,...,C N) or a plurality of the electricity storage elements (C 1,...,C N) connected in parallel; or the series degree is 1 if all of the electricity storage elements (C 1,...,C N) are connected in parallel in the two-terminal circuit, the charging method comprising: a first step (S102, S103) in which the electricity storage elements (C 1,...,C N) are connected to configure the two-terminal circuit having the series degree of 2 or larger and each of the electricity storage elements (C 1,...,C N) are charged by injecting a current into the two-terminal circuit; a second step for changing a connection of the electricity storage elements (C 1,...,C N) to reduce the series degree of the two-terminal circuit; and a third step (S108, S103) for changing the connection of the electricity storage elements (C 1,...,C N) to increase the series degree of the two-terminal circuit and charging each of the electricity storage elements by injecting a current into the two-terminal circuit, characterized in that: the connector includes switches to change a connection state of the electricity storage elements (C 1,...,C N) to configure the two-terminal circuit having the series degree S (S=1, 2,..., N); and after the first step, the second step and the third step are executed alternately a plurality of times. the series degree is a number of unit circuits (U 1,..., Us) connected in series, each of the unit circuits (U 1,..., Us) being composed of a single electricity storage element (C 1,...,C N) or a plurality of the electricity storage elements (C 1,...,C N) connected in parallel; or the series degree is 1 if all of the electricity storage elements (C 1,...,C N) are connected in parallel in the two-terminal circuit, the charging method comprising: a first step (S102, S103) in which the electricity storage elements (C 1,...,C N) are connected to configure the two-terminal circuit having the series degree of 2 or larger and each of the electricity storage elements (C 1,...,C N) are charged by injecting a current into the two-terminal circuit; a second step for changing a connection of the electricity storage elements (C 1,...,C N) to reduce the series degree of the two-terminal circuit; and a third step (S108, S103) for changing the connection of the electricity storage elements (C 1,...,C N) to increase the series degree of the two-terminal circuit and charging each of the electricity storage elements by injecting a current into the two-terminal circuit, characterized in that: the connector includes switches to change a connection state of the electricity storage elements (C 1,...,C N) to configure the two-terminal circuit having the series degree S (S=1, 2,..., N); and after the first step, the second step and the third step are executed alternately a plurality of times. a first step (S102, S103) in which the electricity storage elements (C 1,...,C N) are connected to configure the two-terminal circuit having the series degree of 2 or larger and each of the electricity storage elements (C 1,...,C N) are charged by injecting a current into the two-terminal circuit; a second step for changing a connection of the electricity storage elements (C 1,...,C N) to reduce the series degree of the two-terminal circuit; and a third step (S108, S103) for changing the connection of the electricity storage elements (C 1,...,C N) to increase the series degree of the two-terminal circuit and charging each of the electricity storage elements by injecting a current into the two-terminal circuit, characterized in that: the connector includes switches to change a connection state of the electricity storage elements (C 1,...,C N) to configure the two-terminal circuit having the series degree S (S=1, 2,..., N); and after the first step, the second step and the third step are executed alternately a plurality of times. the connector includes switches to change a connection state of the electricity storage elements (C 1,...,C N) to configure the two-terminal circuit having the series degree S (S=1, 2,..., N); and after the first step, the second step and the third step are executed alternately a plurality of times.