To provide a technique for measuring a state of stress by objective symptoms having a correlation with stress in a mobile terminal device. In order to the above object, a program is provided, and a mobile terminal device reads and executes the program to perform: a video-on step for enabling a moving image capturing function of the mobile terminal; a light-on step for enabling a light disposed at an image capturing side of the mobile terminal; a pupil recognition step for recognizing pupils of animal eyes from an image that is being captured, wherein the animal eyes include human eyes; and a pupil change calculation step for calculating a pupil change, wherein the pupil change is a change in a dilation level of the recognized pupil over time.