Objective: More frequent use of robot technology in the field of rehabilitation is driving the need for smaller, less cumbersome devices. The objectives of the present study were to evaluate and compare quantitatively the upper limb function of chronic stroke patients before and after therapeutic electrical stimulation using a newly developed rehabilitation robot. Methods: Five stroke patients (3 men, 2 women; mean age: 66.4 ± 9.6 years; time since stroke: 36.0 ± 52.9 months) in the sub-acute and chronic phase of stroke-induced hemiplegia (induced by cerebral hemorrhage in four and by cerebral infarction in one; Brunnstrom stages III-V) participated in the study. None of them had any secondary motor neuron dysfunction or unstable disease control. Before and after 15 min of therapeutic electrical stimulation for repeated finger flexion and extension, participants performed reaching movements while moving the rehabilitation robot with their affected hand. Assessment parameters included Maximum swerve, Average speed, and smoothness of movements, as calculated by Jerk cost X (right-left direction) and Jerk cost Y (forward-backward direction). Results: All patients were able to use the rehabilitation robot to perform the reaching movements. Clear differences were observed before and after therapeutic electrical stimulation for Maximum swerve and Average speed in the X direction, and there was a tendency for Jerk cost X to differ before and after therapeutic electrical stimulation. In contrast, there were no significant differences in either Jerk cost Y or Average speed in the Y direction before and after the stimulation. Conclusion: The immediate effects of therapeutic electrical stimulation in chronic stroke patients can be quantified using our newly developed rehabilitation robot. Successful quantification of the effects of therapeutic electrical stimulation in stroke patients using smaller robotic systems could revolutionize the rehabilitation of these and other patients suffering from motor dysfunction or paralysis.