In this study, a muscle volume sensor was developed to estimate the human behavior for its application to bioengineering and synchronous signal collection. The sensor is easily manufactured at a low cost. In addition, its wearability is good, and it can measure the human motion intent using a simple algorithm. This study tested the developed sensor, verified the test results, and applied the sensor to an actual wearable robot to further verify its effectiveness. The results of this study can allow the application of the sensor for a gait assistance device, to the upper and lower extremities, and to medical and industrial equipment.