Superstring theory is a good candidate for a unified theory of all interactions including gravity, and quarks and leptons as well as the Higgs particle. We study particle physics and cosmology, which can derived from superstring thoery. Superstring thoery predicts six-dimensional space, which must be compact, in addition to our four-dimensional spacetime. Geometrical aspects of compact space determine which type of paticle appears and theri properties. We study superstring theory on compact space, which realizes our world and derive their predictions.