Dynamic viscoelastic, creep and steady shear flow measurements are made on a polymer blend melt with a phaseseparated bicontinuous structure. 3D structures at quiescent, constant-stress and constant-shear-rate states are observed by a high-contrast X-ray computerized tomography (CT) after quick quenching of each sample. At the quiescent state, the frequency dependence of the storage modulus at 200 o C shows a power law behavior with the exponent of 0.84. In the shear rate range (at the small shear stress s = 100 Pa) where partial relaxation of the interface of the blend is possible, a peculiar plate-like pattern in the deformed bicontinuous network is observed in the through view of the X-ray CT image. At higher shear rates (at the higher shear stress s = 1000 Pa) where the interface relaxation is suppressed, another peculiar short plate-like pattern appears in the edge view. When the shear rate in the steady shear flow is equal to the average shear rate in the creep test, a very similar deformed pattern of the interface is observed.At the macroscopic shear strain of 3.2 in the creep test at 100 Pa, the observed strain of the deformed bicontinuous network has a distribution and the majority are much smaller than the strain expected from the affine deformation assumption. An average orientation angle of the deformed network at the shear strain of 3.2 corresponds to the angle given by the affine deformation of the shear strain 1.35.