To provide a stabilized subgrade and pavement structure having a water holding property, effective in maintaining water environment, excellent in durability, and also effective in suppressing and effectively using industrial waste.

A stabilized subgrade 2 comprises mainly a subgrade soil, solidification agent, and completely burned bottom ash. Its composition is 3 to 30% in solidification agent by weight and 5 to 15% in completely bottom ash by weight relative to the subgrade soil. Also, it comprises a premixture in which the solidification agent is mixed with the completely burned bottom ash beforehand, and the mixing ratio of the solidification agent to the completely burned ash is 5:5 to 8:2. Thus, a pavement structure 1 contains the completely burned bottom ash in a permeable subgrade 3.