A vehicular power supply device to be applied to a vehicle includes an electric storage unit group, a charger, first and second switches, and a switch controller. The electric storage unit group includes a first electric storage unit and a second electric storage unit having higher internal resistance than the first electric storage unit. The charger is coupled to the electric storage unit group and charges one or both of the first electric storage unit and second electric storage unit. The first switch is provided between the first electric storage unit and the charger and controlled between an on state and an off state. The second switch is provided between the second electric storage unit and the charger and controlled between an on state and an off state. The switch controller controls the first and second switches based on a temperature of the electric storage unit group.