We assessed the impact of working parameters of Z056 Bizon Super on the quantity and quality losses of seeds during soya harvesting. We investigated soya of Merlin variety cultivated in Leszczany (51°021 N; 23°602 E). We found out that the lowest total quantity losses of soya (11.6%) occurred at the working speed of a harvester of 4 km·h^-1, slightly higher (11.78%) at the speed of 2.5 km·h^-1, and the highest (12.41%) at the speed of 6 km·h^-1. We reported the lowest macrodamage of soya seeds (7.8%) at the working speed of a harvester of 6 km·h^-1, slightly higher (9.3%) at the speed of 4 km·h^-1 , and the highest (10.3%) at the speed of 2.5 km·h^-1. We reported the highest purity of seeds (92.3%) in the harvester tank at the speed of 2.5 km·h^-1, slightly lower (90%) at the speed of 4 km·h^-1, and the lowest (89.3%) at the speed of 6 km·h^-1. Taking into consideration a statistic insignificance of differences between the total losses which occur at the working speeds of ZO56 Bizon Super harvester assumed for research, we may find it useful for harvesting soya seeds of Merlin variety within the speeds of 2.5-6 km·h^-1 at the losses of seeds below 12.5%. However, these losses are high.