High power diode laser surface treatment was applied to the R260 grade steels with different processing temperatures which are 1.100 oC, 1.200 oC and 1.300 oC at the laser power of 1.750 watt with scanning speed of 6mm/s. to search the influence of these processing temperatures on both residual stress and fatigue behaviour. It was found that while untreated sample had – 501 MPa residual stress, about twofold increase occurred in the laser treated samples. The fatigue test results showed that increase in processing temperature plays an important role on fatigue behaviour and residual stress is one of the factors affecting fatigue mechanism.