A searching apparatus includes a memory unit which stores transposed indexes representing appearing positions of all n-grams in plural pieces of document data subjected to searching and appearing frequencies, an n-gram extracting unit that extracts all n-grams extractable from a searching character string, a smallest-frequency deriving unit which refers to the appearing frequency of the n-gram represented by the transposed index, and derives an n-gram with the smallest appearing frequency among all of the extracted n-grams, a searching n-gram selecting unit that selects, from all extracted n-grams, a plurality of searching n-grams which form the searching character string and include the n-gram with the smallest appearing frequency, and a document specifying unit that specifies, based on the plurality of selected searching n-grams and the appearing position of the searching n-gram represented by the transposed index, document data including the searching character string among the plural pieces of document data.