A charger comprising: a battery accommodating unit including a first contact and a second contact configured to be respectively in contact with electrode terminals of a battery accommodated therein; a high-potential power supply line and a low-potential power supply line to which power for charging the battery is supplied; a connection switching circuit (SW1-SW4) capable of switching between a first connection state in which the first contact is connected to the high-potential power supply line and the second contact is connected to the low-potential power supply line and a second connection state in which the second contact is connected to the high-potential power supply line and the first contact is connected to the low-potential power supply line; and a control device for controlling the connection switching circuit to acquire a battery voltage of the battery and perform charging control on the battery, characterized in that the control device is configured to: determine whether the battery voltage of the battery exceeds a predetermined set voltage and perform normal charging without performing pre-charging when an absolute value of the battery voltage has already exceeded the set voltage before the pre-charging is started, and otherwise, to perform the pre-charging on the battery in the first connection state, and when the battery voltage does not exceed the predetermined set voltage, to switch the first connection state to the second connection state and perform the pre-charging on the battery, and when the battery voltage exceeds the set voltage, to perform the normal charging on the battery. a battery accommodating unit including a first contact and a second contact configured to be respectively in contact with electrode terminals of a battery accommodated therein; a high-potential power supply line and a low-potential power supply line to which power for charging the battery is supplied; a connection switching circuit (SW1-SW4) capable of switching between a first connection state in which the first contact is connected to the high-potential power supply line and the second contact is connected to the low-potential power supply line and a second connection state in which the second contact is connected to the high-potential power supply line and the first contact is connected to the low-potential power supply line; and a control device for controlling the connection switching circuit to acquire a battery voltage of the battery and perform charging control on the battery, characterized in that the control device is configured to: determine whether the battery voltage of the battery exceeds a predetermined set voltage and perform normal charging without performing pre-charging when an absolute value of the battery voltage has already exceeded the set voltage before the pre-charging is started, and otherwise, to perform the pre-charging on the battery in the first connection state, and when the battery voltage does not exceed the predetermined set voltage, to switch the first connection state to the second connection state and perform the pre-charging on the battery, and when the battery voltage exceeds the set voltage, to perform the normal charging on the battery.