Effects of plasma nitriding on the surface characteristics of tool steels have been investigated using wear tester, micro-hardness tester and scanning electron microscope (SEM) Commercial SKD 11 and SM45 alloy were used as specimens and were plasma nitrided using a plasma nitriding equipment for 5 hr and 10hr at $500^{circ}C$. Microstructure and phase analysis were performed using SEM and XRD. It was found that plasma nitriding for lour at $500^{circ}C$, compared with plasma nitriding for 10hr at $500^{circ}C$, had a thick nitrided layer and produced a layer with good wear resistance and hardness as nitriding time increased. SKD11 alloy showed that wear resistance and hardness decreased, whereas surface roughness increased, compared with SM45 alloy.