In recent years, it has been reported that the mural paintings of Torazuka Tumulus in Ibaraki prefecture might have faded. Dew condensation can be one of the reasons for this degradation phenomenon. In order to investigate the influence of dew condensation on mural paintings, laboratory experiments were conducted in the present study. For the experiments, test pieces reproducing the structure of Torazuka mural paintings were prepared. A test piece was composed of a tuff stone, white substrate layer and red pigments. Two test pieces were set in a closed space where the relative humidity was kept at 100%, and one of the test pieces was cooled by using a Peltier module device to make dew condensation occur on its surface. Dew condensation on the surface of the test piece was identified by measuring weight and water content of the test piece as well as the water transfer in the vicinity of the surface of the test piece. The influence of dew condensation on the substrate layer and pigment was investigated by comparing photographs taken before and after the experiments. However, no influence was recognized in these experiments.