A design efficiency is improved by enabling existing design resources to be utilized. A circuit design system includes a required specification input unit inputting required specification for designing a circuit, a computerized model conversion unit converting design information of an existing circuit into electronic data, a knowledge DB unit storing the design information of the existing circuit which is converted into the electronic data by the computerized model conversion unit, by converting the design information into a knowledge DB, a component DB unit storing information of a component which is used in a circuit, a circuit generation unit acquiring information which is obtained by converting the design information of the existing circuit into the knowledge DB and is stored in the knowledge DB unit, and the information of the component which is used in the circuit and is stored in the component DB unit, on the basis of the required specification which is input from the required specification input unit,
