This contribution deals with an evaluation of soil structure by the unconventional method of fractal analysis. The soil is represented as a pore medium with statistically self-similar structure which represents a fractal structure. The fractal dimension is presented as decisive representative of the structural properties of soil. The fractal dimension is a non-integer number which expresses degradation of soil structure which was caused by pores. This number includes comprehensively the modification of structural properties of soil induced by arbitrary influence. The fractal dimension of clay-loam and sandy-clay soil was related to the activity of factors which represented the influence of exactly defined tillage practices (conventional, reduced and direct seeding) in the depths of 0-3 and 6-9 cm. The intensity and statistical significance of individual factors were determined by analysis of variance. The effects of tillage practices on the modification of surface soil structure represented by fractal dimension and the influence of the tillage depth and the locality were confirmed.