Change in the light interference in film samples of isopropylbenzene was studied in the supercooled liquid (SCL) state. Samples were originally formed as glass by vapor deposition on a cold substrate and the intensity of laser light reflection from them was monitored as the temperature was raised with a constant rate up to the region of the SCL state above the glass-transition temperature. Two types of periodic changes in the light intensity were observed in the SCL state. One was attributed to the interference condition change accompanying the structural relaxation from the low-density SCL to the equilibrium SCL state, and the other was due to the gradual expansion of the high-density SCL. Analysis of the latter change revealed that the initial density of the high-density glass was larger than that estimated in our previous paper.