It was appeared that the evaluation of optimum diameter depends on the size of the arch contacting with the cylinder. In this study, the influence of grip position of the cylinder in the hand on the sensory evaluation of the easiness of the grasp with one hand and with both hands was investigated. In case of the cylinder attached on the boundary between the little finger and the palm, i.e., MP grip, the optimum diameter evaluated as the most easiness to grip was around 20mm. On the contrary, in the case that the cylinder is grasped in the arch formed with index finger and the thumb, the evaluated optimum diameter was around 30mm to 40mm, and it was around 40 mm to 50mm, in the case of grip with both hands. It was appeared that the evaluation of optimum diameter depends on the size of the arch contacting with the cylinder. In addition, it was revealed that the sensitivity of the evaluation is higher in the active grasping than in the passive grasping having cylinders from others.