1. A computer-readable recording medium storing therein an information retrieving program that causes a computer to execute: acquiring a document to be searched and having a hierarchical structure; generating a path schema related to the acquired document; receiving input of a retrieval keyword, a retrieval condition for the retrieval keyword, and a retrieval equation specifying a retrieval range for the retrieval keyword; generating a single automaton that includes a hierarchy retrieval automaton that retrieves a hierarchy of the generated path schema and a hit keyword retrieval automaton that retrieves a hit keyword satisfying the input retrieval condition for the retrieval keyword, the single automaton making state transition between a hit hierarchical node at which the hit keyword in the hierarchy retrieval automaton is present and a set of nodes representing the hit keyword; retrieving, from the document and using the generated single automaton, the hit keyword within the retrieval range; and outputting a retrieval result obtained at the retrieving.