The social climate for women studying STEM subjects is changing, but the proportion of women taking STEM subjects in Japan is small. Only 27.9% of university students in the department of science is women in 2019. In this study, we used an online survey to investigate whether randomly providing three types of gender equality information increased the motivation of junior high school students to choose STEM subjects and the motivation of their parents to support that choice. Information on STEM, especially about social equality, and information on math stereotypes and STEM occupations, increased students’ motivations for studying STEM. This suggests that providing gender equality information is an effective way to change students’ attitudes toward STEM.