To provide a floor surface construction technology capable of constructing a concrete floor surface having extremely high strength without generating embrittlement and detachment on a surface of solidified concrete.

A hardening layer on a superficial layer section of concrete is constructed by: first spreading a concrete modifying agent over a concrete surface C2 which has a plurality of grooves 53 thereon formed by scratching the concrete surface before solidification with a roughening member 52 of a floor surface construction device 10; then compacting the concrete surface by rolling and pressing the same with a rolling compaction device; and pressure leveling and surface smoothing of the concrete surface with a floor surface finishing device when the concrete surface is moderately cured. Because laitance on the surface of the concrete is buried into the concrete in a manner that diffuses and infiltrates the laitance together with the concrete modifying agent, a dense hardening layer produced in a chemical reaction between calcium in the concrete and the modifying agent is formed on the superficial layer section of the concrete.