The study aims at verifying the direct and indirect effects on the prejudice against the homosexuality, based on a survey conducted with 954 university students majoring in social welfare. As a result of causal analysis of the variables by structural equation models, the notable findings are as follows: First, perceptions of equality and advocacy attitudes have no direct effects on the prejudice against the homosexual, however, those influence on it through the full mediation effect of the prejudice against the mentally disordered people. Second, while among people with high spheres of control, the perception of equality has a full mediation effect on the prejudice against the homosexual through the prejudice against people with mental disorder, people with low spheres of control show that advocacy attitudes has a full mediation effect on the prejudice against the homosexual through the prejudice against mentally disordered people. Therefore, the related direct and indirect effects on the prejudice against the homosexual are varied according to the level of spheres of control, the moderation effect of spheres of control are verified. In conclusion, social welfare students' prejudice against the homosexual does not directly influence by their perception of equality and advocacy attitude, however, the prejudice is reduced according to how they perceive people with mental disorder in a proper way as a mediation effect. Some practical implications are discussed based on the study's findings. Individuals' level of spheres of control should be considered when the program is developed to reduce discriminative perception to the homosexual.