To provide a concrete columnar sleeper and rotation preventing member having an equivalent property to a wood sleeper and rotation preventing member, prevented from being soiled and lowering a commercial value, and capable of exhibiting a long service life.

The sleeper 1 has a rectangular cross section and has a predetermined length. The rotation preventing member 27 is formed in a shape of a block wherein at least a flat side surface forms an acute angle with respect to a flat bottom surface. Both of the sleeper 1 and the rotation preventing member 27 are formed by mixing polyethylene, polypropylene and a foaming agent in a ratio of 59.99 to 80 pts.wt., 19.95 to 40 pts.wt. 0.01 to 0.05 pts.wt., respectively, and then by heating and melting the mixture.