Stroke is the sudden onset of neurological deficits due to a presumed local disturbance in the blood supply to the brain, producing motor and sensory impairments. Stroke rehabilitation comprises a variety of approaches to recover functional problems. Physical therapy intervention focuses on the recovery of functional abilities (e.g. gait and balance abilities). Currently, various approaches to treat motor impairments represent repetitive practice of active movement in paretic limbs, leading to beneficial effects induced from positive neuronal plasticity. The electroencephalography (EEG) is an electrophysiological monitoring method to record electrical activity of the brain. Mu wave (μ wave) is the greatest power increased or decreased while performing the movement tasks at the sensorimotor cortex. Decrease in the μ wave has been called as desynchronization, which appears during the observation and execution of goal-directed actions, reflecting mirror neuron function. Various physical therapy approaches are effective tools to improve functional abilities after stroke. Almost study has focused on measurements of functional abilities to demonstrate therapeutic effects of treatment methods. The measurements using EEG introduces the cortical change during treatment. This study provides beneficial information for the use of EEG, including theoretical background and the measurement method of EEG. These efforts should provide a basis to demonstrate to effects of physical therapy in stroke rehabilitation.