Disclosed is a technique using an electric vehicle. The technique enables a user to set the operation plan of the electric vehicle and the price of electricity used to charge/discharge an electric vehicle battery. The electric vehicle battery is charged, or the electric energy charged in the electric vehicle battery is collected, according to the set information. Accordingly, it is possible to charge the electric vehicle battery at the price approved by the user under variable pricing of electric energy. When the price of electricity increases or there is no operation plan of the electric vehicle, the electric energy stored in the battery is collected to operate electric devices or resell the stored electric energy to an electric power company, thereby obtaining economic benefit. As the spread of electric vehicles are extended, it can be expected to save a considerable amount of electric energy throughout the whole society.