1. A computer-readable recording medium storing therein an information search program that causes a computer to search for text items described in a text file, the information search program causes the computer to execute: receiving input of a search keyword; searching an index file for a writing keyword that includes the search keyword, the index file including writing keywords described, for respective entries, in an order identical to the order in which the text items are described in the text file; identifying an entry that corresponds to the writing keyword retrieved at the searching; and outputting the identified entry.