This study assumes that science textbooks are the cause of women's inactive achievement in science textbooks which give the first consideration to men. That is why women have inactive achievement in science compared with men. Therefore, this thesis focuses in masculinity in science textbooks and then searches gender unequality. To analyze these issues, with 8 volumes of elementary school's science textbooks, 6 volumes of middle school's science textbooks and 18 volumes of high school's science textbooks, I analyzed contents about masculinity in science textbooks.The findings of this thesis are as follows; First, the process of textbook compilation appeared in gender inclination. Textbook compilers' gender distribution was masculinity and at the compilation moment, men who are from all facilities such as elementary school, middle school, high school and university, compiled textbook with inclination. Second, textbook contents were selected out masculinity by gender preference. Textbook contents are field and subject of science, those are adequate to men's concern and interest. Third, in curriculum system, according to the example of experiment observation, an phraseology of gender meant different meaning by every sentence. Forth, role models showed masculinity with male scientists introduced in textbooks and the different role of man and woman in the picture. Fifth, in transmitting gender role, according to scientific activities in the picture and illustration, scientific activities were differently shown between man and woman and focused in masculinity in role allotment.In a conclusion, the findings of this thesis show that sincere educational equality starts from equal educational opportunities. Therefore the cause of gender unequality in education can be argued with a variety of ways but perfect gender fairness is accomplished from textbooks as basic material in school education.