This paper presents a soft manipulator which mimics the muscle structure of an octopus arm and its operation by the master-slave method by using a wearable interface. The soft manipulator consists of a rubber structure and McKibben artificial muscles arranged in axial and oblique directions. This manipulator has high safety and shape adaptability and realizes smooth and continuous movement like the octopus arm such as bending and twisting. For the intuitive operation of the manipulator, the wearable interface using flexible strain sensors is developed. It is easy to wear on the human arm with high comfortability because it consists only of soft materials and stretches easily with following the arm motion. We can operate the soft manipulator by using the motions of the wrist and forearm as an operation input. The soft manipulator can move following the arm motion of the operator, and it shows the high possibility to conduct actual tasks.