The purpose of this study is to investigate the effect of ultrasound therapy on calf muscle spasticity of stroke patients. Ten patients who were diagnosed with stroke by a specialist in rehabilitation medicine were divided into two groups by random assignment method. The control group received a 10-minute ultrasound placebo effect after general physiotherapy. In the experimental group, ultrasound therapy was given for 10 minutes after general physical therapy. In this study, muscle tone was assessed using MAS(modified ashworth scale), balance was assessed using TUG(time up amp go), and gait was assessed using a 10m walk test. There was a significant difference between the experimental group and the muscle tone, balance, and gait. However, there was no significant difference in the control group. There was a significant difference between the groups in balance and gait, but not in muscle tone. Ultrasound therapy should be adapted to reduce spasticity and improve function in stroke patients.