PROBLEM TO BE SOLVED: To provide a fine aggregate for a lightweight fire resistant concrete useful for producing the lightweight fire resistant concrete excellent in fire resistant properties. SOLUTION: The fine aggregate which contains moisture Wi inside, whose surface is covered with surface water Wo and whose diameter is 5 mm or less is obtained by removing and classifying ultra-fine particles by washing fine particulate ash. When the fine aggregate is dried at a temperature of 670-730°C, the surface water Wo is removed and voids S are generated by removing a part of the inside moisture Wi. When it is heated to 800-850°C, the ratio of an amorphous component is increased and the voids S which contain residual moisture inside is remained. The bubbles W at the surface layer of the fine aggregate are plugged with a coating material and furthermore a film C whose viscosity is increased by adding cement and water and by rising pH with OH - ion released from the cement is formed at the surface of the fine aggregate and finally the fine aggregate whose moisture content is 3-5 wt.% is obtained. COPYRIGHT: (C)2005,JPO&NCIPI