It is the object of the present invention to provide asynchronous circuit design tools for those engineers who are versed in standard hardware description languages (HDLs), which is widely used in industry mainly for synchronous circuit design, to design asynchronous circuits with relative ease. To accomplish the object, the asynchronous circuit design tools of the present invention include a translator for transforming a code written in an asynchronous circuit design language, which is based on a standard HDL and includes minimal primitives for describing the communications between asynchronous circuit blocks or processes, into a code written in a standard HDL, which is originally developed for synchronous circuit design. The codes transformed into the standard HDL can be functionally verified by using commercially available simulators, which are originally developed for verifying synchronous circuit design.