The aim of this research are to describe the effectiveness of worksheet which improve creative thinking skills of student through stoichiometric material. The creative thinking skills which practiced in this study are fluency, flexibility, originality, and elaboration. The properness of worksheet was assessed based on validity, practicality and effectiveness. This was a quantitative research that used one group pretest-posttest design. Worksheet was implemented on class X-MIPA 2 Gedangan Senior High School Sidoarjo in academic year 2016/2017. Data obtained through tests. The instruments of this study is creative-thinking-skills-test and mind-mapping-test sheet. Data were analyzed descriptively. The results show that (a) worksheet was effective help students to master the concept of stoichiometry and (b) also improve the creative thinking skills of all student by getting the n-gain score with high category. This improving caused by the developed of student worksheet is valid and very valid category, as well as each of the learning phases in worksheet has been well to excellent implemented.Based on these result, it was concluded that the worksheet based guided inquiry and mind mapping was proper to improve the creative thinking skills of the students through stoichiometric material.