Superplastic punch forming of sheets is simulated by a finite element method to obtain the optimal punch speed and the related deformed shapes. The punch forming has an advantage of guaranteeing the desired accuracy inside a product and controlling the thickness of a deformed sheet more accurately than blow forming. The finite element code developed is associated with the contact algorithm and the control algorithm of punch speed for the optimum forming. The simulation demonstrates that the variation of the thickness in a blank sheet affects the punch speed and the final distribution of the thickness in a product. The analysis proposes that a ring-typed thickness controller is very effective in controlling the thickness of a deformed sheet appropriately.