Incremental forming is a relatively novel sheet forming process, in which parts can be formed without the use of dedicated dies. In this paper, the influence of the process parameters (tool diameter, step size, feed rate, existence of a die, forming methods, and kinds of tool path) on surface roughness in the case in which parts are processed by incremental forming was discussed. Al 1050 material is used in the experiments. A table of orthogonal arrays is used to design the experiments and the ANOVA method is employed to statistically analyze the results. The obtained results show that the process parameters of tool diameter, step size, and the existence of a die have a significant effect on the surface roughness, whereas the feed rate, forming methods and kinds of tool path are insignificant.