  We report on neutron scattering studies of a rare earth intermetallic
compound ErNi$_{2}$Ge$_{2}$. Polarized neutron scattering experiments revealed
that the magnetic ordered moment ${\bm m}$ lies in ab-plane. Taking account of
a lack of the third higher harmonic reflection, ErNi$_{2}$Ge$_{2}$ is
considered to have a helical magnetic structure. The magnetic scattering
profiles along the $[100]^{\ast}$- and the $[110]^{\ast}$-directions are well
described by the sum of Gaussian and modified-Lorentzian terms, even far below
$T_{\scriptsize N}$, indicating that short-range orders coexist with a
long-range order. Interestingly, the modified-Lorentzian-type diffuse
scattering is not present in the profiles along the $[001]^{\ast}$-direction.
The anisotropy of the diffuse scattering suggests that the short-range-order
consists of one dimensional long-range helices along the c-axis.
