  We construct Lorentz invariant and gauge invariant 1PI effective action for
closed and open superstrings and demonstrate that it satisfies the classical BV
master equation. We also construct the quantum master action for this theory
satisfying the quantum BV master equation and generalize the construction to
unoriented theories. The extra free field needed for the construction of closed
superstring field theory plays a crucial role in coupling the closed strings to
D-branes and orientifold planes.
