The invention provides a content retrieval device and a content retrieval method which can assist a user in modifying character strings used for retrieval so as to improve the retrieval efficiency and reducing the operation amount of the user in the retrieval process. The content retrieval device comprises a character string display unit, a composite character string judgment unit, a cursor position detection unit, a unit word detection unit, a substitute word display unit, a character string reconstruction unit and an expected content retrieval unit. The substitute word display unit obtains a unit word, namely, a substitute word which can replace an object unit word according to other unit words, namely, adjacent unit words, adjacent to the object unit word in the retrieval character string, and displays the substitute word to be selected by the user. When the user selects the substitute word, the character string reconstruction unit replaces the object unit word with the selected substitute word so as to form a new retrieval character string and display the new retrieval character string, and the user can retrieve the expected content.