Experimental study on enhancement of chloride volatilization of Zn, Pb and Cu from molten fly ash less than 75 pm in particle size soaked with hydrochloric acid was conducted in the temperature range 873-1123 K holding time of 1-120 min and reduced pressure lower than 101.3 kPa to 1.3 kPa. As a result, it was found that the volatilization ratio of ZnCl2, PbCl2 and CuCl in 1.3 kPa were 1.5-3.0 times higher than those obtained in 101.3 kPa. The volatilization ratio of these heavy metal chlorides rapidly increased with the heating temperature, under reduced pressure. At a higher heating temperature of 1123 K, almost 100% of ZnCl2 and PbCl2 were volatilized within 1 min, in the reduced pressure of 1.3 kPa. The volatilization of the heavy metal chlorides at a constant temperature increased with a decrease in the pressure. In particular, the volatilization of ZnCl2 and CuCl was significant when the pressure was reduced below saturated vapor pressure of ZnCl2 and CuCl. However the volatilization of PbCl2 was increased over saturated vapor pressure of PbCl2. It was found that KPb2Cl5 was formed in the residue during heating under reduced pressure.