  The thermal inflation is the most plausible mechanism that solves the
cosmological moduli problem naturally. We discuss relic abundance of superheavy
particle $X$ in the presence of the thermal inflation assuming that its
lifetime is longer than the age of the universe, and show that the long-lived
particle $X$ of mass $10^{12}$--$10^{14}$ GeV may form a part of the dark
matter in the present universe in a wide region of parameter space of the
thermal inflation model. The superheavy dark matter of mass $\sim 10^{13}$ GeV
may be interesting in particular, since its decay may account for the observed
ultra high-energy cosmic rays if the lifetime of the $X$ particle is
sufficiently long.
