A computer is allowed to execute an information acquisition process that acquires a file expressing information on pins used in respective ports provided in each block of a logic circuit to be redesigned and information indicating connection relationships between the ports (#2); execute a multiplexer disposition process that, based on the file, classifies pins of output ports of a block into a number of pin groups that is less than the number of pins, and disposes a multiplexer having a function to multiplex a signal output from each pin classified in the same pin group (#11, #13); and execute a demultiplexer disposition process that, based on that file, disposes a demultiplexer having a function to demultiplex signals that have been output from output ports of a block and multiplexed by the multiplexer, and a function to output each demultiplexed signal to input ports of respective input destination blocks (#12, #13).