<p>Soft grippers have attracted attention as a method for grasping objects with various shapes, sizes, and weights in an enveloping grasp with a simple structure. Soft grippers with various structures have been proposed, such as multi-finger soft grippers using pneumatic actuators and fingerless grippers such as jamming grippers. However, they have been developed with a focus on a variety of objects that can be grasped. Therefore, when the shape error of the object to be grasped is limited to a certain range, there is still room for the optimization of the shape of the grasping part and other aspects. In this study, we propose a soft gripper driven by a spherical actuator that offers a high degree of freedom in gripping part design. The spherical actuator part can open and close widely for any width, thickness, number, and shape of gripping parts at the rim, allowing the design to be optimized according to the characteristics of the object to be grasped. We propose a method for designing a soft gripper specialized for each grasped object by taking advantage of this degree of freedom. This proposal contributes to the development of a specialized approach focused on enveloping grasps for specific objects, in contrast with a generalized approach aimed at grasping a wide variety of objects using a single system.</p>