Based on our previous reports, stabilizing the surgeon's arm with an intraoperative armrest is linked to improved precision of microsurgical and endoscopic procedures. We developed the robotic intelligent surgeon's arm supporting system iArmS, which automatically follows the surgeon's arm and fixes it at an adequate position. iArmS has 3 states-free, hold, and wait-which can be carefully chosen automatically as follows: In free state, the armholder follows the surgeon's arm. In hold state, iArmS supports the surgeon's arm weight by fixing the armholder. In wait state, the surgeon can move his or her arm away from the armholder. Also, the surgeon can change the armrest position while looking through the microscope and can continue the microsurgical procedure while holding surgical instruments. From February 2015 to January 2017, iArmS was used in 108 microsurgeries at 3 of the authors' institutions by 14 board-certified neurosurgeons, including the authors. After using iArmS, to quantify neurosurgeons' satisfaction, a scaling evaluation guide based on visual analog scales was designed to be completed by contributing neurosurgeons, including authors. iArmS decreased fatigue and reduced hand trembles experienced by surgeons. Continuous accurate motions of microinstruments were performed without any difficulties. There were no complications related to use of iArmS. iArmS allows continuous precise manipulations that provide high-quality surgical results in neurosurgical techniques. Moreover, iArmS is a useful automatic tool for holding and following the surgeon's arm.