This report describe a thickness distribution finding problem and an initial shape finding problem for a gas-inflatable reflector. The problems are formulated as the problems to find the thickness distribution and the initial membrane shape whose deformed shape under prescribed pressure becomes a paraboloid of revolution. The deflection analysis is performed by the finite element method. In the optimization, the objective function is the surface profile error between the paraboloid and the inflated shape of membrane. The discrete distribution of optimum thickness is obtained in the former case and the initial shape is obtained in the later case.