The electric power supply control apparatus for a vehicle executes a driving prioritizing mode in which a supply of driving electric power is prioritized over a supply of temperature controlling electric power, and a temperature control prioritizing mode in which the supply of the temperature controlling electric power is prioritized over the supply of the driving electric power. While the modes are switched over, the apparatus controls the driving electric power or the temperature controlling electric power so that a sum of the powers stays at an upper limit value or smaller.