A system and method for managing energy of an electric vehicle are provided to calculate a necessary amount of energy based on battery characteristics and a user's schedule, and control charging and discharging of the electric vehicle using power information provided by a smart grid. The system includes a cloud server configured to collect a schedule from a user and store and generate the user's schedule information, an energy management device configured to calculate necessary energy based on the received schedule information of the user, set charging information based on power network state information received from a power supplier and the calculated necessary energy, generate a charging request signal based on the set charging information, and store electric energy, and a charging unit configured to transfer the electric energy to the energy management device based on the received charging request signal.