In our study, a soft robot arm consisting of McKibben artificial muscles and silicone rubber has been developed. This robot arm can perform bending and twisting motions by applying pneumatic pressure to several artificial muscles. Since the robot arm is made of flexible materials only, it has high flexibility and shape adaptability. Therefore, the soft robot arm is expected to play an active role in situations involving people and fragile objects, such as medical care, nursing care, and agricultural work. In addition, the arm-worn wearable interface has been developed as an operating system for the soft robot arm. It is made by attaching flexible strain sensors to a highly elastic arm cover worn by an operator. This interface detects the bending of the operator's wrist and the twisting of the forearm, and the detected motions are used as inputs for the bending and twisting motions of the soft robot arm. This enables the intuitive manipulation of the soft manipulator. In this report, flexible strain sensors are placed on the soft robot arm for master-slave feedback control. The number of sensors and their fundamental locations in the soft robot arm and the wearable interface are the same, and they are arranged in one-to-one correspondence. By comparing the corresponding sensor values, master-slave feedback control is realized.