Dynamic birefringence and dynamic viscoelasticity of polymer brush type polystyrene polymacro-monomer, PM, consisting of only styrene unit were measured over a wide frequency region including the glass transition region. The stress-birefringence relationship elucidated that the stress relaxation of the PM proceeded through three processes. The fastest one was attributed to the glassy component responsible for the high glassy modulus. This process was found to be essentially the same as that for the ordinary linear polystyrene, 1-PS. The second one was assigned to be the reorientation process of the side chains. The viscoelastic segment size of the side chains was estimated to be about half of that for 1-PS. This difference in size could be attributed to the reduction of nematic effect. The slowest one was assigned to the reorientation of the main chain. This process was described with the beads-spring theory with the viscoelastic segment about 3 times larger than that for 1-PS. The large viscoelastic segment size of the main chain was fairly in accord with the large Kuhn segment size determined by light scattering experiments on the PM in dilute solution.