To suppress various expenses such as development cost and manufacturing cost associated with production of a printed board while suppressing occurrence of a problem of EMC (electromagnetic compatibility).

The pattern loop shape calculation method for printed board, for evaluating a loop shape of a pattern formed by a power supply network or GND (ground) network in a printed board, comprises first processing for selecting an object network for loop detection among the power supply network or GND network; second processing for extracting a loop point for each object network selected by the first processing; third processing for selecting a loop to be detected from the loop points extracted by the second processing; and fourth processing for calculating an adaptation ratio of the loop selected by the third processing with a predetermined condition.

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