A power source device chargeable by an external power source, comprising: a first power storage device chargeable and dischargeable, and connected to a first node; a load connected to a second node; a first voltage converting unit configured to convert voltage between said first node and said second node bi-directionally; a second power storage device chargeable and dischargeable, and connected to a third node; a second voltage converting unit configured to convert voltage between said third node and said second node bi-directionally; a power transmitting unit configured to transmit power received from said external power source to said first node; and a control unit configured to control said first and second voltage converting units ( 12A, 12B); wherein said control unit is configured to control said first and second voltage converting units ( 12A, 12B) such that voltage of said third node attains to a desired charging voltage and thereby charges said second power storage device, characterized in that the power source device further comprises a first connecting unit ( SMR2A) capable of shutting off connection between said first power storage device and said first node; and a second connecting unit ( SMR2B) capable of shutting off connection between said second power storage device and said third node; wherein said control unit is configured to, at the time of charging said second power storage device, set said first and second connecting units to shut-off and connected states, respectively, said power transmitting unit is capable of selecting a connection destination from said first and third nodes (N1, N3); and said control unit is configured to set, when said power transmitting unit is connected to said third node, said first and second connecting units (SMR2A, SMR2B) to connected and shut-off states, respectively, to control said first and second voltage converting units ( 12A, 12B) such that voltage of said first node attains to a desired charging voltage and thereby to charge said first power storage device. a first power storage device chargeable and dischargeable, and connected to a first node; a load connected to a second node; a first voltage converting unit configured to convert voltage between said first node and said second node bi-directionally; a second power storage device chargeable and dischargeable, and connected to a third node; a second voltage converting unit configured to convert voltage between said third node and said second node bi-directionally; a power transmitting unit configured to transmit power received from said external power source to said first node; and a control unit configured to control said first and second voltage converting units ( 12A, 12B); wherein said control unit is configured to control said first and second voltage converting units ( 12A, 12B) such that voltage of said third node attains to a desired charging voltage and thereby charges said second power storage device, characterized in that the power source device further comprises a first connecting unit ( SMR2A) capable of shutting off connection between said first power storage device and said first node; and a second connecting unit ( SMR2B) capable of shutting off connection between said second power storage device and said third node; wherein said control unit is configured to, at the time of charging said second power storage device, set said first and second connecting units to shut-off and connected states, respectively, said power transmitting unit is capable of selecting a connection destination from said first and third nodes (N1, N3); and said control unit is configured to set, when said power transmitting unit is connected to said third node, said first and second connecting units (SMR2A, SMR2B) to connected and shut-off states, respectively, to control said first and second voltage converting units ( 12A, 12B) such that voltage of said first node attains to a desired charging voltage and thereby to charge said first power storage device.