In this study, the effect of cutting conditions on surface integrity was investigated in micromilling of magnesium alloy (AZ91). Microtool diameter, cutting speed, feed rate, and depth of cut parameters are used. These variables were investigated at three different levels with the Taguchi L9 experimental design method. The least-best objective function was used. As a result of the experiments, surface roughness values were obtained. It has been determined that surface roughness values and depth of cut are effective parameters. After evaluating the results obtained, variance and regression analyses were performed. Based on the analysis of variance, 58.73% feed rate was found for the 1.0 mm diameter tool, on the other hand, for the 0.8 mm diameter tool, the depth of cut was found to be an effective parameter with 53.6%.