In order to study the dynamics of the semiconductor-metal transition in liquid selenium, we have measured the transient absorption spectra of liquid selenium after illuminating with a pulsed laser. We have observed the disappearance of the optical gap when the pulsed laser with the intensity of 15 mJ/pulse illuminates liquid selenium at 350℃, which means that the photoinduced semiconductor-metal transition occurs. The time variation of the spectra after the illumination suggests that the structural change occurs accompanying the semiconductor-metal transition.