  We prove the solvability in Sobolev spaces of the conormal derivative problem
for the stationary Stokes system with irregular coefficients on bounded
Reifenberg flat domains. The coefficients are assumed to be merely measurable
in one direction, which may differ depending on the local coordinate systems,
and have small mean oscillations in the other directions. In the course of the
proof, we use a local version of the Poincar\'e inequality on Reifenberg flat
domains, the proof of which is of independent interest.
