A layout method of a semiconductor integrated circuit includes five steps. The first step is of extracting a wiring crowding place where wiring lines are crowded as compared with a predetermined condition, after carrying out a routing in a region where a placement of circuit elements is carried out. The second step is of generating routing prohibition regions where a routing is prohibited in an area including the wiring crowding place. The third step is of carrying out a routing by bypassing the routing prohibition regions. The fourth step is of deleting the routing prohibition regions. The fifth step is of carrying out a re-routing. The generating step includes: calculating a size and an interval of the routing prohibition regions based on a rate for generating a routing prohibition region in the area in each wiring layer, and generating the routing prohibition regions in the area on the basis of the calculating result.