  We propose a way to determine the pairing state of the iron pnictide
superconductors exploiting the momentum (Q) scan of the neutron scattering
data. We investigate the spin susceptibility in the s+- and s++ superconducting
states for various doping levels using the effective five-orbital model and
considering the quasiparticle damping. The peak position of the intensity
shifts from the position on the line Qx = pi to that on the line Qy = 0 as the
doping level is decreased from electron doping to hole doping. We find that the
Q-dependence of the ratio of the intensity in the superconducting state to that
in the normal state is qualitatively different between the s+- -wave and s++
-wave pairings. We propose to investigate experimentally this ratio in Q-space
to distinguish the two pairing states.
