In this paper, mechanical ratcheting of 6-4 brass under steady axial stress and cyclic shear load is investigated experimentally. In the experiments, the strain rate is controlled to be 200 × 10^<-6>[1/s] and the number of cycles is 0〜100cycles. The amount of the increasing ratchet ratcheting strain is formulated precisely as the function of the steady stress, the cyclic strain amplitude and number of cycle for less than 100 number of cycles. The calculation method is suggested for estimating the amount of the ratchet strain that finally converges by normalizing the relationships between ratcheting strain and the direction of plastic strain increment vectors.