We present a novel approach to accelerating isosurface polygonization by exploiting the power of graphics processor unit (GPU), along with the Marching Cube (MC) algorithm. Efficient use of GPU in our approach allows us to accelerate cube index computation for the entire cubes of input data set, which is the dominant process in MC. Our approach is quite unique in that it generates information for geometric construction of the data set in pixel shading hardware. The techniques in our approach are similar to those in a multipass method in that the multiple rendering passes are used to render the final image. Then the result of previous pass is fed into geometry pipeline in our approach, whereas it is fed into an image pipeline in the multipass method. Our experimental results illustrate very well that our approach has many applications for realtime generated volume data such as metaballs and numerical simulation results, without imposing any conditions on the input data set.