In this study, we developed a vertical articulated robotic arm for laparoscopic surgery and proposed a method of controlling the robot. The robotic arm operates surgical instruments around a virtually fixed remote center of motion (RCM) calculated from the robot kinematics. The robotic arm has six degrees of freedom and is driven by pneumatic actuators. The features of the pneumatic actuators of compactness, high backdrivability, and low heat generation allow the robotic arm to be moved passively by the human hand and prevent the risk of heat accumulation in the drape. We made the upper arm and forearm lightweight by mounting the pneumatic actuators on the base of the robot. The joint angles are controlled by pneumatic servo systems. The inertia of the forearm and upper arm was estimated by measuring the joint angles. We also proposed variable gain control of the yaw joint to compensate for changes in inertia. We experimentally confirmed that the variable gain improves the controllability of the robot and improves its operability around the virtual fixed RCM.