An object of the present invention is to prevent occurrence of an
unconnected terminal during arrangement and connection, shorten the time
required for automatic arrangement and connection, improve a yield, and
improve the properties of a cell. A recognized object-of-wiring thinning
cell (minimum-rule cell) is temporarily replaced with a preferred-rule
cell. Since a block has a free region devoid of a cell, an event that a
replaced preferred-rule cell interferes with an adjoining one and is not
separated from the adjoining one by a predetermined pitch will not take
place. Even when the replaced cell interferes with the adjoining one,
since the block has the free region devoid of a cell, the cell can be
moved to a position at which it will not interfere with the adjoining
one. An event that the cell is not separated from the adjoining one by
the predetermined pitch will not take place. When all object-of-wiring
thinning cells have been treated, reconnection is performed. When
processing is terminated, a region of the block is modified.