In this research, we study a method for measurement of multiple users' breathing by using far infrared (FIR) imaging. We first propose a method to discriminate the regions including each user's face. Here, FIR images were binarized and discriminant analysis was used in order to find strict boundary. By applying this process, one FIR image is divided into two sub images in which each image includes one user's face. We next apply a method to extract the regions including nasal cavity from each regions which was capturing one user's face. Here, we extract the regions including nasal cavity from each sub image which was capturing a single user's face. From the results of extraction, we calculate the temperatures in nasal cavity, and estimate qualitative flow velocity in nasal breathing. According to the result of experiments, the accuracy of the estimation was ranged from 40% to 91%.