The purpose of this research is to draw some implications for reducing gender differences in educational achievement of mathematics by inquiring those in mathematics-related attitudes. For this purpose, this article analyzed the gender difference in mathematics-related attitudes of the elementary, middle, and high school students. Also, mathematics-related attitudes according to achievement levels was analyzed. The findings of this study are as follows. Firstly, in the scores on mathematics-related attitudes, male students were significantly higher than those of female students. Secondly, in the evaluation of the subordinate factors of mathematics-related attitudes, gender differences were shown a little bit larger in the areas of interest and self confidence than in the area of perception of mathematics value regardless of grades. Thirdly, in all schools, the higher achievement level is, the higher the score of mathematics-related attitudes is. Lastly, gender differences on mathematics-related attitudes in advanced level group is bigger than those in other level groups.