To improve a spectacle, and prevent separation of painting by imparting wettability to a painting surface in a design structure of an interlocking formed on a painting surface whose surface is exposed to a road surface is colored.

A painting surface 2 is formed on the obverse in an instantly mold-separated interlocking 1 by in-plant pre-site operation work. The interlocking 1 is instantly molded by a separable mold into a brick-shaped concrete product whose both side surfaces 10 are formed in a waveform shape. The painting surface 2 is formed on a surface 11 exposed to a roade surface, and wettability is imparted to the painting surface 2. At painting time, in a condition where a large number of interlockings 1 are juxtaposed on the surface 11, a large number of interlockings 1 are simultaneously colored by one time painting work by painting paint. Coloring painting is performed by spraying painting using spray paint.