In a pattern evaluation method of determining whether a pattern formed on a photomask is acceptable, an aberration parameter of an image quality evaluation apparatus for determining a pattern image intensity in transferring a pattern formed on a photomask onto a wafer is acquired. An acceptance criterion value used in determining whether an abnormal pattern of the photomask including the effect of aberration of the image quality evaluation apparatus is acceptable is set through a lithographic simulation using the acquired aberration parameter. Then, using the image quality evaluation apparatus, an image intensity of the abnormal pattern of the photomask and an image intensity of a normal pattern corresponding to the abnormal pattern are obtained. It is determined whether the difference between the two acquired image intensities is within the set acceptance criterion value.