The traditional stress state is composed of two normal stresses and a shear stress in the two dimensional space, and three normal stresses and three shear stresses in the three dimensional space. Therefore, six stressometers at least are necessary to determine the stress state at a point in space. Based on the stress state theory, a stress apparatus that can detector the three dimensional stress states is devised. The apparatus is made up of six one-way stressometers which are disposed at the edges of a tetrahedron. The tetrahedron is regular of all even arbitrary shaped in theory considering rational, logical, stability and conveniently. The mapping transformation, from the traditional stress state to the stress state illustrated by the edges of the tetrahedron is constructed. Furthermore, the traditional stress state can be derived from the data collected by the three-dimensional stress apparatus, and causes of errors are analyzed.