The objective of this study is to propose a robot that is capable of climbing a net by utilising a carabiner-type gripper to ascertain the optimal grasp. In contrast to rigid climbing targets, such as fences, nets are flexible objects, and the position of the grasping target is not fixed. It is therefore necessary to confirm the grasp prior to commencing the climbing motion on the net. A gripper mechanism with a variable annular component is proposed, in which the degree of rotation of the variable component is detected to confirm whether the grasped object has entered or exited the annular component. Furthermore, the attachment of a servo motor to the variable component enables the mechanism to grasp objects in a manner analogous to existing grippers. The proposed climbing robot is demonstrated to be capable of stable ascending and descending movements on the net by verifying the grasp at each climbing operation.