Purpose The purpose of this study was to investigate the effect of rotator cuff strengthening exercises on the shoulder joint range of motion and gross motor in patients with weakened rotator cuff muscle strength of the paralyzed shoulder due to stroke. Methods A total of 25 stroke patients were conducted, including 12 in the experimental group and 13 in the control group. The experimental group provided rotator cuff strengthening exercises, and the control group provided treatment to increase shoulder flexibility and mobility. Both groups were treated 3 times a week for 4 weeks after the common rehabilitation treatment routine. A ROM test using a goniometer was used to measure the shoulder joint range of motion, and a Box and Block Test(BBT) was performed to measure the shoulder movement. The evaluation was conducted twice in total: the pre and post intervention evaluation within the two groups and the pre and post intervention evaluation between the groups. Results In the evaluation before and after the intervention in each group, both groups showed a statistically significant increase in shoulder joint range of motion and shoulder groping ability. In the pre and post intervention evaluation between groups, the experimental group showed a statistically significant difference in shoulder flexion(p<.01), shoulder abduction(p<.05) and shoulder gross motor(p<.001) compared to the control group. Therefore, it is judged that the rotator cuff muscle strengthening exercise of the paralyzed shoulder of stroke patients can be applied to improve the shoulder joint range of motion and the ability to move the shoulder.