To improve walking performance and to reduce weight by using a calcium silicate plate as a lower layer member, and using a continuous porous mixture formed by hardening rubber chips with adhesive resin, as an upper layer member.

A lower layer member A is formed of a calcium silicate plate 1 and provided at the lower face with drain grooves 2 opened to four side faces. An upper layer member B is formed of a continuous porous mixed plate 3 formed by solidifying rubber chips with adhesive resin. Rainwater during rainfall enters continuous porous clearances of the upper layer member B, flows in all directions therefrom, enters clearances 4 between the opposed side faces of the calcium silicate plates 1, 1 through side face parts 3a, 3a and is guided to a drain part of a concrete foundation bed C via the drain grooves 2 of the lower face of the calcium silicate plate 1 and eliminated. Impulsive sound during walking can therefore be reduced, water is well drained, and walking performance is excellent because of having moderate resiliency while being unslippery. In addition, the whole weight is reduced.