An inquiry approach in teaching science has been advocated by many science educators for the past few decades, and most elementary and secondary science curricula have incorporated it in varying degrees. It has been proven in recent studies, however, that there exists considerable discrepancy between the expectation of outcomes of the inquiry approach and the actuality. This in part implies that there is a somewhat urgent need for the systematic evaluation of the approach in teaching science. The purpose of this study is to develop a comprehensive instrument for evaluating inquiry teaching approaches embedded in science curricular materials. To develop a more valid and reliable instrument a set of empirical data was used in the developmental procedure, and most of the previous studies regarding inquiry teaching method and inquiry evaluation were consulted. The inquiry evaluation method developed in this study, called the Scientific Inquiry Evaluation Inventory (SIEI), is composed of three parts: (1) analyzing and coding each science process task of inquiry activity; (2) evaluating each inquiry activity as a whole; and (3) evaluating each science laboratory curriculum as a whole. The first part of the instrument consists of twenty science process categories and thirty subcategories grouped into four sections: (1) gathering and organizing data; (2) interpreting and analyzing data; (3) synthesizing results and evaluation; and (4) hypothesizing and designing an experiment. The science process categories are arranged according to the level of difficulty, psychological level of thinking, degree of creativity demand, and the model of the process of scientific inquiry, which is also developed in the study. The second part of the instrument contains four evaluation scales of inquiry activity: (1) competition/cooperation scale; (2) discussion scale; (3) openness scale; and (4) inquiry scope scale. And the last part consists of three methods for evaluating a science laboratory curriculum as a whole: (1) inquiry pyramid; (2) inquiry index; and (3) difficulty index. The instrument is designed to be used by teachers, science curriculum developers and science education evaluators for the purpose of diagnosing the nature and appropriateness of scientific inquiry introduced in secondary science curricular materials, especailly in laboratory work and field work.