A pattern producing method includes specifying a first pattern and a
second pattern obtained by modifying the first pattern, specifying a
correction area based on the second pattern, in a part of an area
including the first pattern and the second pattern, producing at least a
part of the first pattern, which is included in the correction area, as a
correction target pattern, producing a part of the first or second
pattern, which is not included in the correction area, as a correction
reference pattern, correcting the correction target pattern on the basis
of the correction target pattern and the correction reference pattern,
and producing a pattern based on the corrected correction target pattern
and the second pattern.