A clock routing design method enables a routing design for each hierarchy while paying an attention to each layout hierarchy to which a branch of a clock signal system extends and considering a whole chip. In the clock routing design method, a clock signal line is routed between a plurality of receiver terminals over a plurality of layout hierarchies while considering an equal-delay branch point yielding equal delays of a clock signal at the receiver terminals, the clock signal line is then routed between the equal-delay branch point positioning between the plural receiver terminals and the driver terminal. The clock routing design method is applicable to a layout design of wire patterns, cell, etc. on LSIs, printed circuit boards and the like.