A solvable two-dimensional conformally invariant midisuperspace model
for black holes is obtained by imposing spherical symmetry in four-dim
ensional conformally invariant Einstein gravity. The Wheeler-DeWitt eq
uation for the theory is solved exactly to obtain the unique quantum w
ave functional for an isolated black hole with a fixed mass. By suitab
ly relaxing the boundary conditions, a nonperturbative ansatz is obtai
ned for the wave functional of a black hole interacting with its surro
undings.