Inquiry skill is the most important factor in the development of the scientific processes of prospective science teachers. The objective of this study is to research the effect of using inquiry-based activities on the development of scientific process skills of prospective science teachers. The research group of the study consists of students studying in their third year of science teaching department at Ordu University (n=32). Inquiry-based activities were conducted on prospective teachers for three months within the nature of the science course. Mixed research design, which uses quantitative and qualitative research methods together, was used in this study. As the quantitative data collection tool, a 36-item of scientific process skills scale, which had Cronbach Alpha internal consistency coefficient of 0.70, was used as pre-test-post-test. SPSS 17 program was used for data analysis and "t-test for dependent samples" was conducted. In the qualitative part of our research, "content analysis" approach was used. Descriptive analysis was conducted on the content of interviews with prospective teachers and observation reports. It was concluded through quantitative and qualitative research analyses that inquiry-based science activities significantly increased scientific process skills of prospective science teachers positively. It is recommended that researchers who conduct studies to increase scientific process skills should use inquiry-based activities.