Heat-treated pine wood is commonly utilized in the furniture and construction sectors, with milling being a key technique to enhance the surface quality of these products. To investigate the milling surface damage mechanism of heat-treated wood, a milling test of pine wood was conducted after different heat treatments, and the effects of heat treatment temperature and cutting parameters (cutting depth and feed per tooth) on cutting force and surface roughness were analyzed. The experimental and analytical results of these cutting tests indicate that higher heat treatment temperature resulted in reduced wood strength, leading to a reduction in cutting force as the heat treatment temperature increased. Additionally, the brittleness of wood increased with increasing heat-treatment temperature, which caused more burrs and wood tissue fragments to appear on the machined surface, resulting in increased surface roughness. Increasing cutting depth from 0.1 mm to 0.5 mm raises cutting force and surface roughness for untreated and heat-treated wood. For depth, force increases by 35.5% to 15.32% and roughness by 75.8% to 84.7%. For feed speed from 0.2 mm/Z to 0.6 mm/Z, force increases by 37.55% to 34.56% and roughness by 58.38% to 91.4%. This study investigates the milling surface damage mechanisms of heat-treated wood, filling the gap in the literature that has focused on the effects of cutting parameters on surface roughness without examining surface damage mechanisms, providing a theoretical basis for optimizing the processing technology of heat-treated wood.