The present status of the research on superconductivity of a heavy fermion compound UPt3 is reviewed. We emphasize the interplay between the antiferromagnetism and unconventional superconducting state, which is deeply related to the origin of the superconducting double transition phenomenon found in this system. After giving a brief review on various heavy fermion superconducting materials in order to put the UPt3 problem in a general context, a problem which is ultimately to identify the superconducting pairing symmetry, we introduce various experimental data and rearrange them to provide the constraints on the theories that followed. Then we review the two scenarios based on the two-dimensional and one-dimensional representations. We study comparatively these scenarios, concluding that the former scenario is less possible than the latter.