As a new surgical device to accomplish both maximum tumor removal and functional preservation, Laser Induced Liquid Jet (LILJ) has been developed. Since 2011, the multicenter clinical trial has commenced intended pituitary tumor removal in 7 hospitals, all of whom were assigned to high volume center of pituitary tumor treatment in Japan, and they encountered over 100 cases in total. From the questionnaire filled by the surgeons, the surgeons desired the usability of LILJ hand piece to be improved. In this study, we designed and attached a new grip adapter for hand piece, and evaluated it in terms of weight center control, moment, and robustness against disturbance input in ergonomic experiments. In the results, the hand piece with the new grip adapter accomplished the reduction of the applied force by each finger from 1.4 to 0.4 mN (29%) and the error distance by mistaken fire from 19.5 to 9.1 mm (47%). Hence, the stability and operability of the LILJ hand piece were progressed.