AbstractThis article focuses on the plane milling of thermally modified birch wood while taking into account technological parameters that have substantial effects on the processed wood surface’s average waviness profile deviation (Wa). The milling process was affected by the cutting speed, which varied from 20 to 60 m/s, with a feed rate of 4, 8, and 11 m/min. The results obtained on the set of thermally modified test specimens, were compared with the results obtained on test specimens without heat treatment. The surface finish was measured using various milling parameters. The material removal was 1 mm per pass. The results indicate that the thermal processing of wood did not significantly influence the arithmetic average deviation of the roughness profile (Ra). Cutting speed and feed rate had the most significant effects among the monitored factors. The lowest arithmetic average deviation of the roughness profile (Ra) was determined at a feed rate of 4 m/min and cutting speed of 40 m/s. An increase in cutting speed led to a decrease in the average roughness, while increased feed rate had the opposite effect.