The novel design with the adaptability prevents from unexpected stimulus current for medical safety, since the safety is the prime concern for human use. The prototype of the stimulus driver circuit for micro-stimulator used in implantable device is presented in this paper. For epilepsy control, the target of the driver is to output 30-μA stimulus currents, as the tissue impedance varies within 20-200 kΩ. The driver composed of the output stage, adaptor, and control block, has been integrated in a chip. Fabricated in a 0.35-μm 3.3-V/24-V CMOS process, the performances of this novel design have been confirmed. The averaged power consumption of the driver was only 0.24-0.56 mW under 800-Hz stimulation rate.