PURPOSE: To obtain a raw material pitch which can easily produce coke having a uniform, fine mosaic optical structure by controlling the molecular weight distribution so that it contains a suitable amount of a high molecular component insoluble in quinoline and it is brought into an optically isotropic state.

CONSTITUTION: A raw material pitch for a high-density isotropic carbonaceous material optically isotropic completely when observed under a polarizing microscope, which contains at least 80wt.% toluene-insoluble matter and 30-70wt.% quinoline-insoluble matter comprising an α-resin of condensed polycyclic aromatic hydrocarbon containing a high molecular component that can be readily made soluble in quinoline by chemical reduction and has a molecular weight distribution of 10,000 to 100,000 in terms of polyethylene glycol as determined by GPC after reduction. The pitch can easily produce coke having an optically uniform, fine mosaic structure, serving as the raw material of a high-density isotropic graphite material used as a graphite material for a nuclear reactor, an electrode material for electric discharge machining, a bearing material for machinery, etc.