A method for designing a logic circuit and a CAD program which allow a logic circuit with desired performance to be designed in a short period of time by suppressing the elongation of a logic design period for achieving a circuit area, an operating speed, power consumption, and the like as target specifications are provided at low cost. Shorter-period and lower-cost design is accomplished by allowing a user to use a high-performance logic synthesis CAD program at no charge if he only checks circuit characteristics resulting from synthesis and collecting a fee if the user is satisfied with the resulting circuit characteristics and intends to use a gate level logic circuit. In a design phase which receives a register transfer level or operation level logic circuit and synthesizes a gate level logic circuit, desired circuit characteristics are obtainable in a short period of time at low cost.