This study developed questionnaires designed to measure student centrality and cohesion in small groups. Student centrality and small group cohesion were defined in terms of their effect on and relation to other students in a science learning network. Drafts of the questionnaire items were made, based on such operational definitions, and the questionnaire instrument composed of 6 items through 4 pilot tests and 5 validation verification. Application of the questionnaire to 168 students (42 small groups) in the sixth grade of elementary school showed that the students’ centrality value (0~2) reached 0.293 on average and the small group cohesion value (0~1) 0.319, respectively. Unlike cohesion that showed normal distribution, the centrality values showed a positively skewed distribution toward the left. The majority of the students tested turned out to possess centrality of an ordinary level. This study devised methods of utilizing centrality and cohesion, which are relationship features of students in a small group in scientific inquiry activities. The questionnaire that was developed measured small group centrality and cohesion is expected to apply to school education.