To provide a pitch type graphitized staple fiber aggregate suitable for preparing a thermally conductive composition excellent in thermal conductivity in the thickness direction.

The pitch type graphitized staple fiber aggregate is characterized in that the pitch type graphitized staple fiber is immobilized into a three-dimensional random shape with a sizing agent, wherein 0.1-5 pts.vol. sizing agent are included to 100 pts.vol. pitch type graphitized staple fibers.