1. A non-transitory computer-readable recording medium having stored therein a compression program that causes a computer to execute a process comprising: reading a plurality of character strings from a compression target file; examining order information whether there are any concatenated character strings that contain a certain character string in the plurality of character strings with an order of the certain character string, in a compression dictionary, the compression dictionary correlating a plurality of concatenated character strings with a plurality of compression codes respectively, each of the plurality of concatenated character strings include a plurality of character strings, the order information indicating whether there is a specific character string in the compression dictionary with an order of the specific character string; and searching the compression dictionary utilizing the plurality of character strings when the order information indicates that one or more concatenated character strings include the certain character string.