The anomaly in the anomalous Nernst effect (ANE) was observed for a C1b-type NiMnSb half-Heusler alloy thin film deposited on a MgO (001) substrate. The Nernst angle ({theta}ANE) showed maximum peak with decreasing temperature and reached 0.15 at 80 K, which is considered to be brought by the cross-over from half-metal to normal ferromagnet in NiMnSb at low temperature. This anomaly was also observed for the transport properties, that is, both the resistivity and the anomalous Hall resistivity in the same temperature range.