1. A semiconductor integrated circuit device manufacturing method comprising: exposing a photomask which includes a mask pattern formed in accordance with a circuit pattern verified by a verification method; and imprinting the circuit pattern on a substrate, wherein the verification method comprises: creating simulation patterns on the basis of design patterns; comparing shapes of the simulation patterns with each other; combining, into one group, the simulation patterns on the basis of the comparison result, values of differences among the shapes of the simulation patterns in the one group being not more than a predetermined value; and verifying information of extracted simulation patterns extracted from the one group, wherein all of the extracted simulation patterns have error candidates.