Brain-Computer Interface (BCI) technology has been of great interest as a potential therapeutic measure for people with severe neuromuscular disorders, thereby enabling them to use their brain signals directly for controlling stimulation of paralyzed muscles. We hypothesized that closed-loop system which links continuous motor-related brain activity measurement to muscle stimulation can modulate sensorimotor nervous system into a physiological state that enables volitional muscle control in severe chronic upper-extremity hemiplegia after stroke. In order to give such conditional feedback in a clinical situation, we developed a wearable semidry-typed electrode for electroencephalogram (EEG) recording as well as an exoskeleton robotic device for finger movement support. Motor-driven support of finger extension movement, combined with electrical stimulation to the extensor digitorum communis muscle, was triggered by motor-related EEG, thus the patients with chronic stroke hemiplegia were allowed to use such a BCI system in an actual pegboard training in occupational therapy. Our pilot study with case series clinical trial confirmed its efficacy BCI device in views of neurological and behavioral improvement in paretic hand function.