In many worksites, there are some tasks that each worker’s location will affect the work efficiency, the safety of work, the frequency of mistakes, the physical and mental workload, etc. The relationships between the location of people and the efficiency of the work, etc. have been investigated using personal trajectory data. The data is obtained by people tracking methods. Although the tracking methods have been developed by many researchers over the decades, several issues remain. One of the biggest issues is the lack of capability of individual recognition. Another of the biggest issues is to protect the privacy of the people involved in the tracking. In this paper, first, the existing methods of people tracking are surveyed and the necessary requirements for tracking the people are shown. And then, a new people tracking method using invisible visual markers made of a near infrared LED is proposed. We attempt to recognize multiple people by our method. It is shown that two peoples can be successfully tracked separately in our laboratory, and the privacy of the person is protected.