Viscoelastic nature of asphalt mixture depends on testing method, (creep, rate of strain and dynamic), and binder property. Generally, it is said that gumphalt mixture have more elastic nature than straight asphalt mixture, and it's nature is recognized by static test. But it have never known that dynamic test is also useful one about testing the stress relaxation of gumphalt. So, dynamic test of gumphalt mixture was performed to exhibit it's nature and fatigue property in this paper. It is possible to divide deformation of asphalt mixture between elastic deformation and viscous flow, and former is usually called-solid and latter is also called-liquid. In static test (or long loading time), deformation of asphalt mixture looks like viscous flow, and in dynamic test (or short loading time), it's deformation nearly equal to elastic deformation. But, these tendency depends on binder property, proportion of asphalt mixture and temperature too. In previous report, author examined dynamic property in straight asphalt, and explained it's fatigue property and viscoelastic nature. In this paper, dynamic test of gumphalt mixture is performed and then, viscoelastic nature, fatigue property and dependency of temperature are compared with straight asphalt mixture. Many investigators are interested in dynamic property of asphalt mixture, but few of them have ever adopted square wave. In dynamic test by square wave, it is difficult to analyze theoretically.