AbstractLinear stability of a thin melt layer on metal walls after a plasma disruption was investigated in order to clarify the mechanism of the roughness formation which is observed in an experimental work by Ogawa et al. (1992). Stability characteristics in terms of a thermocapillary (Marangoni) instability are found to be consistent with the experimental results. A relationship between the critical Marangoni number and the crispation number parametrized by the Prandtl number and the Bond number was obtained to predict the occurrence of the roughness formation on the resolidified surface.