Abstract. We propose a new method to estimate human change of concentration from multiple camera views of the human. In our method, human state of concentration is observed as self-load, defined as energy injected in a period to keep and manipulate his/her body. If a person is concentrating to a certain task, he/she will brace himself/herself for better results, and energy consumption will increase. To confirm our idea, we developed a method to calculate self-load from multiple view of the human. We conducted an experiment in which test subjects have different level of complexity of task. Self-load of the subjects showed the positive correlation with the complexity of the task. We have convinced that self-load can be used to characterize the concentration of person being observed.