Summary: The temperature and quark mass dependence of the topological susceptibility is analyzed in a random matrix model. A model combining random matrices and the lowest Matsubara frequency is known to describe the chiral phase transition of QCD qualitatively, but at finite temperature it suppresses the topological susceptibility in the thermodynamic limit by the inverse of the volume. We propose a modified model in which the topological susceptibility at finite temperature behaves reasonably. The modified model reproduces the chiral condensate and the zero-temperature result for the topological susceptibility of the conventional model, and it leads to a topological susceptibility at finite temperature in qualitative agreement with lattice QCD results.