Computer

A computer capable of easily obtaining RTL of a TOP circuit after a block circuit is separated out of the TOP circuit. A port information input unit inputs the port information of the TOP circuit described in RTL, and the port information of block circuits composing the TOP circuit, from a user. A separation information input unit inputs separation information specifying a block circuit to be separated out of the TOP circuit, from the user. A separation port information creation unit creates separation port information after the block circuit is separated, by changing the port information of the TOP circuit and the block circuits based on the port information of the block circuit to be separated according to the separation information. An RTL rewriting unit rewrites RTL of the TOP circuit from which the block circuit has been separated, based on the separation port information created by the separation port information creation unit.