A vehicle power source device includes a first group that includes a first battery and a first load group which is connected with the first battery, a second group that includes a second battery or includes the second battery and a second load group which is connected with the second battery, a third group that includes a starting device which starts an internal combustion engine and a capacitor, a first switch that is provided between the first group and the second group, a second switch that is provided between the second group and the third group, a third switch that is provided between the first group and the third group, and a control unit that performs control to turn the first switch off, the second switch off, and the third switch on in a case where the internal combustion engine is started.