1. A defect predicate expression extraction device extracting predicate expressions representing defects from text data related to use of products, comprising: a predicate modifying expression storage unit for detecting defect expressions, wherein said predicate modifying expression storage unit stores at least one of predicate modifying expressions representing suddenness and predicate modifying expressions representing repeatability; a defect predicate expression candidate extraction unit for detecting, in said text data, expressions matching each of the said predicate modifying expressions stored in said predicate modifying expression storage unit for detecting defect expressions, and extracting, as a candidate for a predicate expression representing a defect, a predicate expression occurring in a neighborhood of each of the said detected expressions in said text data; a predicate modifying expression storage unit for detecting normality expressions, wherein said predicate modifying expression storage unit stores predicate modifying expressions representing normality; a normality predicate expression extraction unit for detecting, in said text data, expressions matching each of the said predicate modifying expressions stored in said predicate modifying expression storage unit for detecting normality expressions, and extracting, as a predicate expression representing normality, a predicate expression occurring in a neighborhood of each of the said detected expressions in said text data; and a defect predicate expression acquisition unit for acquiring, as said predicate expressions representing defects, predicate expressions remaining after said predicate expressions extracted by said normality predicate expression extraction unit are removed from a list of said predicate expressions extracted as candidates for said predicate expressions representing defects.