To utilize a resin products waste in a fibrous state as a flow resistance improver for an asphalt mixture by mixing the waste into the asphalt mixture.

While an aggregate 1 prepared by mixing crushed stones, sand, and stone dust and heating the resultant mixture to 160-180°C is being mixed and kneaded for 5-10 sec in a dry mixer, a regenerated fibrous substance 3 obtained by crushing and thermally melting resin articles (e.g. PET bottles) in an amount of 0.05% (of the total weight of an asphalt mixture being prepared) is homogeneously mixed and dispersed in the aggregate. Thus obtained dispersion is sprayed with asphalt 2 and wet mixed for a predetermined time, giving an asphalt mixture improved in flow resistance. While air is being blown into the mixer 9 with an air blower, the regenerated fibrous substance 3 is homogeneously dispersed and mixed; then, the resultant mixture is sprayed with asphalt 3 and mixed for about 1 min, thus giving an asphalt mixture containing the aggregate 1 and the regenerated fibrous substance 3 entangled in each other and having improved resistances to flowing, abrasion, and cracks.