Perovskite-type oxides of LaFeO₃ (LFO) have been used as alternatives to precious metals such as platinum for promoting the oxidation of diesel particulate matter. In a previous study, LFO was found to exhibit lower activity than the conventional Pt/Al₂O₃ catalyst for soot oxidation because of its small specific surface area. The purpose of this study is to obtain LFO via an energy-saving combustion synthesis (CS) and to improve the catalytic activity of LFO thus obtained for soot oxidation by subjecting it to mechanical activation. LFO was obtained by CS from La₂O₃, Fe, and NaClO₄ powders and milled using an inclined planetary ball mill at the rotation of 500 rpm for different milling periods ranging from 0.5 to 6 h. The milled LFO samples were characterized by XRD and SEM, and their BET surface areas were measured. Using a thermogravimetric analyzer, the catalytic activities of the LFO samples were evaluated at different temperatures for soot oxidation. The XRD patterns revealed a simultaneous decrease the intensity of the product peaks and peak broadening with an increase in the milling time. This was probably because the degree of crystallinity of the samples decreased with a decrease in the particle diameter. The LFO samples were found to exhibit good catalytic activity for the oxidation of carbon black at temperatures above 400 °C, though their surface area was smaller than that of Pt/Al₂O₃. The LFO powder obtained by using our method might prove to be a suitable alternative to Pt/Al₂O₃ catalysts.