The Black Hole Cosmology that "the universe we observe is the interior of a black hole" was proposed in the 1970's. However, this Black Hole Cosmology is known to have several fatal flaws. In the black hole, singularity exist in the future, whereas in the real universe, singularity exist in the past. And, while the objects inside the black hole are moving toward the singularity, the observed universe is an expanding universe, and it looks completely opposite to each other. Moreover, since black holes are images that decompose humans into atomic units through strong tidal forces, the claim that humans are living inside black holes has not been seriously considered. In this study, I will solve the singularity problem and prove that humans can live inside a sufficiently large black hole. Inside a universe black hole, there is an almost flat space-time larger than the observable universe. Currently, the observable universe is expanding at an accelerated rate because it exists in a region R_obs < R_gs where negative gravitational potential energy is greater than positive mass energy. Therefore, I would like to request new interest and research on Gravitational Self-Energy and Black Hole Cosmology through this study.