To provide a decorative cement-base substrate, having high strength, and more improved in beauty in respect of color, and a decorative cement-base substrate construction method, taking enough construction time and having high degree of freedom in construction.

This decorative cement-base substrate construction method includes: an aggregate resin mixing process of mixing aggregate with a particle diameter of 3-8 mm and a synthetic resin binder to obtain an aggregate resin mixture; an aggregate resin mixture applying process of applying the aggregate resin mixture to the construction surface on the cement-base substrate to form an aggregate resin mixture layer; a slag water-mixing process of mixing a slag mixture made of slag, a curing initiator and sand with water to obtain a slag mixture paste; a slag mixture pasting process of applying the slag mixture paste to cover the aggregate resin mixture layer after the synthetic resin binder of the aggregate resin mixture layer is cured; and a slag mixture paste removing process of removing the slag mixture paste to expose the surface of the aggregate of the aggregate resin mixture layer before the slag mixture paste is cured.