The purpose of this study was to investigate the feasibility and therapeutic effects of a novel concept hand rehabilitation device based on magnetics for subacute stroke patients with hand motor impairment. We developed an end effector type device that can induce various movements of the fingers in accordance with a magnetic field direction using electromagnets and permanent magnets. Subacute stroke patients with hand motor impairments were recruited and divided into two rehabilitation groups. Conventional rehabilitation therapies were also conducted equally in both groups. Active-assisted training of the affected hand was additionally administered for 30 minutes per day for 4 weeks using the developed equipment in the intervention group. Hand motor function and the activities of daily living were evaluated before and after the intervention. The Manual Function Test score significantly increased in the intervention group after 4 weeks of treatment (p = 0.039), and there was a significant difference in the degree of improvement between the two groups (p = 0.016). The scores of the motor Fugl-Meyer Assessment of the upper limb, the Wolf Motor Function Test score and time, and the motor Functional Independence Measure also improved in both groups (all p < 0.05). In addition, the patients in the intervention group showed greater improvements in these outcome measures than those in the control group did (all p < 0.05). An adjuvant rehabilitation therapy using a magnetic based device can be helpful to improve the hand motor function and activities of daily life in subacute stroke patients.