Polypropylene (PP) was ablated using a 248-nm KrF excimer laser with a fluence in the range of 0.4-2 J/cm(2) and at a repetition rate of 10 Hz. It has been found that both photochemical and thermal effects are co-operative during laser ablation process, evidenced by the existence of thermal affected zone (TAZ), together with ablative zone (AZ) and unaffected zone (UAZ) in the ablated crater. Increment of both fluence and the number of pulses leads to a more striking thermal effect, demonstrated by the spatial expansion of rim for PP. Relative importance of photochemical and thermal effects was theoretically discussed.