PURPOSE: To restrain chip exposure data from increasing in processing time and to improve it in interchangeability when a part of a functional block is replaced by a method wherein a data extraction region is provided around the exposure data of the functional blocks laid out, and the data extracted by the data extracting region is used as a reference data for the correction of a proximity effect.

CONSTITUTION: When a functional block 3 is modified or replaced, a part of data stored in functional blocks 1, 2, 4, 7, 8, 10 and 11 provided adjacent to the functional block 3 is extracted by a data extracting region 3a, and the correction of a proximity effect is made to the pattern data of the peripheral part of the functional block 3 using the extracted data. Therefore, the object can be met by correcting only the data of the functional block 3, so that the light exposure data of the whole chip is not required to be reconstructed and consequently a data processing time can be restrained from increasing. The sub-fields of functional blocks may as well be different from each other in size and the functional blocks are improved interchangeability with other blocks of different sizes.