PURPOSE: To provide a character string processor capable of efficiently executing necessary analysis by using relating information between single words concerning a Japanese sentence including a composite word composed of plural relating single words.

CONSTITUTION: The character string processor is provided with a morphemic analyzing means (103) dividing a character string into morphemes and an evaluation means (106) choosing one analytic result by evaluating plural analytic results by the morphemic analyzing means (103). The character string processor is also provided with a relating information holding means (107) holding relating information between the single words and a composite word judgement processing means (106A) judging whether the morphemes divided by the morphemic analyzing means (103) are composite words or not. The evaluation means (106) refers to relating information of a last single word concerning the composite word at the time of referring to relating information at the time of choosing the analytic result.