Recently it has been suggested that neutrinos have nonvanishing mass from both experimental and theoretical investigations. Accelerator experiments and cosmology, however, impose the constraints on mass mv and lifetime τv of vτ (see Fig. 1). As we showed in the previous paper [1], supernova explosion also imposes the stringent constraint on them. The purpose of this paper is to investigate the constraint imposed on mv and τv of vτ from SN1987A.

Tau neutrinos are emitted from the central part of the iron core together with the electron neutrinos because they are also in thermal equilibrium with matter there.