In order to clarify unusual superconducting properties, we have carried out 9Be NMR measurements for a single crystal of UBe13 with Tc ≅ 0.85 K. The NMR spectra under 5 T parallel to [001] crystal axis show no change between Tc(H = 5 T) = 0.41 K and Ta(H = 5 T) = 0.35 K. Below Ta, however, the reduction of the Knight shift was observed. The reduction of the Knight shift of Be(II) is amount to ∼ 0.02 %, which is much smaller than spin part of the Knight shift, Kγ ∼ 0.107 % estimated from electronic specific coefficient γe ≅ 1000 mJ/(K2 • mol). The origin of reduction of the Knight shift cannot be explained by spin singlet superconductivity.