A planar shock wave, which is discharged from the open end of a circular cross sectional shock tube into free space, is diffracted and results in a spherical shock wave. Behind the spherical shock wave a complicated flow is observable. In this paper this axisymmetric shock wave phenomenon was investigated experimentally and numerically. The experiment was conducted in a 25 mm diameter shock tube equipped with double exposure holographic interferometry. In order to evaluate the axisymmetric interferometric fringes the density profile were obtained numerically by solving the integral equation which relates the density distribution with the three dimensional fringe distributions. To simulate the axisymmetric shock diffraction, the Total Variation Diminishing (TVD) finite difference scheme is applied to the Euler equations. The computational results were compared with the evaluated experimental results. A good agreement was obtained between them.