  We investigate classical solutions in closed bosonic string field theory and
heterotic string field theory that are obtained order by order starting from
solutions of the linearized equations of motion, and we discuss the ``field
redefinitions'' which relate massless fields in the string field theory side
and the low energy effective theory side. Massless components of the string
field theory solutions are not corrected and from them we can infer
corresponding solutions in the effective theory: the chiral null model and the
pp-wave solution with B-field, which have been known to be alpha'-exact. These
two sets of solutions in the two sides look slightly different because of the
field redefinitions. It turns out that T-duality is a useful tool to determine
them: We show that some part of the field redefinitions can be determined by
using the correspondence between T-duality rules in the two sides, irrespective
of the detail of the interaction terms and the integrating-out procedure.
Applying the field redefinitions, we see that the solutions in the effective
theory side are reproduced from the string field theory solutions.
