[Purpose] The aim of this prospective, double-blind, randomized, placebo-controlled study was to evaluate the effects of therapeutic continuous ultrasound (US) on patients with rotator cuff disease. [Subjects and Methods] Twenty-two patients were treated with a standard physiotherapy program consisting of a hot-pack, transcutaneous electrical nerve stimulation (TENS), exercises, and US that was supervised by the same physiotherapist. The patients were randomly assigned to either a group that received true US (n=11) or one that received sham US (n=11). [Results] There were significant differences between the pre- and post-intervention UCLA Shoulder Rating Scale and Constant-Murley Shoulder Outcome scores, VAS, and external rotation (ER) peak torque 60°/second values for both the true and sham US groups. However, the between-group differences were not statistically significant. [Conclusion] In patients with rotator cuff disease, physiotherapy interventions effectively treat the pain, improve the clinical status, and increase the muscle strength of the shoulder ER at a low constant angular velocity, with functional improvement being seen immediately after treatment. However, at the end of the intervention, the US had yielded no additional efficacy to the physiotherapy treatment regimen of the patients with rotator cuff disease.