To execute dependency parsing while including a phrasal unit having no modifiee or a phrasal unit related to itself by utilizing not only information of two phrasal units of a modifier and a modifiee but also information of other phrasal units.

A feature string, showing a feature of each phrasal unit in a phrasal-unit string having word information, is generated (s1). A label, showing that a target phrasal unit is related to which phrasal unit in the rear N phrasal units and by which type or that it is not related to the rear N phrasal units, with respect to each phrasal unit is determined by sequence labeling based on a conditional random statistical field for calculating the likelihood of the label of the target phrasal unit from the feature of the target phrasal unit, the features of the rear N phrasal units, and a label of a phrasal unit immediately before the target phrasal unit (s2). A phrasal unit having a modifiee in the rear N phrasal units is determined from each label so as to delete it from the feature string and to convert the label regarding the deleted phrasal unit into dependency information (s3). The sequence labeling and phrasal-unit deletion are repeatedly executed until the number of phrasal units in the feature string is one or less (s4). Labels regarding the remaining phrasal units are converted into the dependency information so as to restore a phrasal-unit string having dependency information (s5).