Abstract
Recent technology on the precise measurement of time and frequency makes it rather easy to detect the relativistic effects. It is, therefore, indispensable to take these effects into account when we conduct such precise measurement. Though the fully understanding of the theory of relativity is not so easy, the effects that appeared in the precise time and frequency measurements is rather restricted and not so difficult to handle with. In this article, we will show the outline of the relativity and try an intimate illustration on most popular four relativistic effects; second Doppler effect, gravitational red shift, Sagnac effect and Shapiro delay.