A material testing apparatus for measuring the biaxial deformation behavior of polymer tube is developed to quantitatively investigate the deformation behavior of polymeric materials. The testing apparatus is capable of applying an axial force and internal pressure to a tubular specimen. A non-contacting strain and shape measurement system consisting of laser micrometers and an area camera is also developed. The biaxial strain components and the radius of curvature in the axial direction of a bulging specimen are measured to perform feedback control of the biaxial true stress components at the center of the bulging specimen. Polyethylene tube with an outer diameter of 17 mm and a thickness of 2 mm is used to make tubular specimens with a length of 110 mm. The specimens are subjected to linear stress paths with true stress ratios of σφ: σθ=1:0, 4:1, 2:1, 4:3, 1:1, 3:4, 1:2, 1:4, and 0:1, where σφ and σθ are the axial and circumferential true stress components applied to a bulging specimen, respectively. Biaxial true stress-strain curves are successfully measured at a nearly constant strain rate of 1×10-3 s-1. The maximum equivalent strain of 0.71 has been achieved at the stress path of σφ:σθ=2:1.