A power supply device includes first and second electric power lines, first and second boost converters, and an electronic control unit. The first and second electric power lines are connected to a load and a battery, respectively. The first and second boost converters each transfer electric power between the second and first electric power lines while changing a voltage of the electric power. The electronic control unit is configured to execute both-side driving when a temperature of the battery is equal to or more than a specified temperature and to execute one-side driving when the temperature is less than the specified temperature. The electronic control unit is configured to drive switching elements of the first and second boost converters with driving signals different in phase to execute the both-side driving, and to drive one of the first and second boost converters to execute the one-side driving.