To prevent peeling-off of a painting by maintaining breathing of concrete by forming quasi-stone shaped divided surfaces by joints on a concrete wall surface by painting the joints with pigment-colored surfaces and painting the quasi-stone with painted colored surface.

An L-shaped concrete block A for L-type retaining wall has a surface of the rising portion 11 which is wholly formed to netlike joints 13, and a quasi-stone surface 14 is formed. And water-soluble pigments are applied to the joints 13 colored with pigments, and various kinds of paints with many colors are painted to the quasi-stone division surface 14; coating transparent wet paint with spraying and brushing and then painting with various color is desired. In this way, breathing of concrete can be maintained through the joints 13 for preventing peeling-off of coats. In addition, painted colored surfaces, pigment colored surfaces and concrete exposed texture can be adopted in various styles, and the joints 13 may be formed in parallel to the longitudinal direction or grid shape, and the wall surface design of the rising portion 11 can be diversified considerably.