In this study, we analyzed the resistible force in grasping by deformation of soft material fingertip focused on the contact area used cylindrical fingertips which have same bending rigidity. Experiments were conducted using soft material fingertip with different hardness and size to acquire each data of tangential force by the force sensor and the contact area by image processing. As a result, we acquired the linear relationship between resistible force in grasping and the contact area rate (the ratio of the contact area when tangential force reached to resistible force to initial contact area). It is suggested that soft material fingertip can give stable grasping against discontinuity changes in the contact areas.