The aim of this study was to evaluate the impact of microbial phytase addition to laying hen diet on the balance of phosphorus, calcium, manganese and zinc. Phytase supplementation caused a decrease in phosphorus excretion by 8% in the group with low-phytase diet and 21% in the group with phytase addition of 1000 FTU (one unit of phytase activity) to a diet. Phytase supplementation increased the retention of phosphorus by 31% in laying hens receiving 500 FTU and 57% in the group with phytase addition of 1000 FTU to a diet, in comparison to the group without enzyme supplementation. The level of manganese in excretion was increased by 18% in the group receiving 1000 FTU phytase, and retention decreased by 24% compared with the control group. Zinc excretion was significantly increased in the group receiving 500 FTU (P È 0.01) and in the group receiving 1000 FTU phytase (P È 0.05). Retention of zinc was lower (P È 0.01) when the birds were fed with feed containing 500 FTU and 1000 FTU phytase (P È 0.05), compared with the control group. No effect on the quantity and retention of calcium excretion was found. There was no impact of phytase supplementation on egg production and egg weight.