Network analysis methods have been applied in many areas such as computer science, social science, biology and physics. In this paper, we apply network analysis methods to the linguistic domain for classifying subjective documents. Particularly, we view that subjective documents are related to one another according to some common subjective words and build a subjective document network of which nodes are documents and of which links represent the similarity between two documents. In addition, we consider that adjectives and adverbs are the two representatives carrying sentimental polarities among parts-of-speeches, and perform experiments for three cases, using adjectives only, adverbs only, and both adjectives and adverbs together. In conclusion, this paper proposes a new method to the subjective document classification problem by applying network analysis methods without requiring linguistic domain knowledge and suggests the possibility of detecting themes among documents rather than binary classification.