This charger 1 is provided with: a battery housing unit 2 including a first contact T1 and a second contact T2 which touch the respective electrode terminals of a battery BAT to be housed therein; a high-potential power supply line 3 and a low-potential power supply line 4 to which power for charging the battery BAT is supplied; a connection switching circuit 5 capable of switching between a first connection state in which the first contact T1 is connected to the high-potential power supply line 3 and the second contact T2 is connected to the low-potential power supply line 4 and a second connection state in which the second contact T2 is connected to the high-potential power supply line 3 and the first contact T1 is connected to the low-potential power supply line 4; and a control device 7 for controlling the connection switching circuit 5 to perform charging control on the battery BAT. The control device 7 performs preliminary charging on the battery BAT in the first connection state and, when a battery voltage VB does not exceed a set voltage VS, switches the connection state to the second connection state and performs preliminary and normal charging on the battery BAT.