There is provided a flow pattern regular expression creating method, a regular expression creating apparatus, and a program enabling provision of a new representation method enabling one-to-one correspondence to a flow pattern. A regular expression creating method of creating a regular expression of a flow pattern in a multiply connected exterior domain with N (N is an integer equal to or larger than 1) holes topologically includes a graph representation creating step of creating a graph representation having one-to-one correspondence to the flow pattern; and a regular expression creating step of creating a regular expression from the graph representation that is created at the graph representation creating step.