In superstring theories, there exist various dilaton and modulus fields whose masses are expected to be of the order of the gravitino mass (Formula presented) These fields lead to serious cosmological difficulties, the so called “cosmological moduli problem,” because a large number of moduli particles are produced as the coherent oscillations after primordial inflation. We make a comprehensive study of whether the thermal inflation can solve the cosmological moduli problem in the whole modulus mass region (Formula presented) predicted by both hidden sector supersymmetry (SUSY) breaking and gauge-mediated SUSY breaking models. In particular, we take into account the primordial inflation model whose reheating temperature is so low that its reheating process finishes after the thermal inflation ends. We find that the above mass region (Formula presented) survives from various cosmological constraints in the presence of thermal inflation. © 1999 The American Physical Society.