Wash chickpeas and black beans thoroughly.
Soak the ingredients in water for at least 8 hours.
Boil the soaked chickpeas and black beans in boiling water for 15 minutes.
Drain and cool the cooked ingredients using a strainer.
Blend the boiled chickpeas, black beans, and water in a blender until smooth.
Strain the mixture once more.
Pour the soy milk into a pot and simmer over low heat for 5 minutes.
Serve the finished soy milk in a cup.