This study was carried out to investigate the effect of dietary phytase on nitrogen and phosphorus excretion of gestating and lactating sows (Yorkshire ${ imes}$ Landrace ${ imes}$ Duroc). Twelve gestating sows and twelve lactating sows were used in this study and were divided into 2 groups (1 control group and 1 treatment group, 6 replications/group) the control group was without phytase and the treatment group was fed with phytase (750 FTU/kg) in the diet, respectively. Body weights of gestating and lactating sows were $208.9{pm}13.8$ kg and $190.5{pm}22.9$ kg, respectively. In gestating sows, feed intake was greater in phytase fed group than the control (P<0.05), but water intake and total excretion were not different between the groups. In lactating sows, feed and water intakes and total excretion were not different between the groups. The N intake of lactating sows was higher in phytase fed group than control (P<0.05) but N excretion ratio was not different. In lactating sows, N intake and excretion and N excretion ratio were not significantly different between the groups. P excretion and excretion ratio in gestating sows decreased by phytase treatment (P<0.05) as compared to control. In lactating sows, N intake and excretion was not significantly different by added phytase (P>0.05). Finally, dietary addition of phytase decreased P excretion in feces of gestating and lactating sows.