To improve cushion property and drain capability by forming a roadbed for a racetrack out of a rubber chip layer by accumulating rubber chips, and sticking a pressure sensitive adhesive to the outer periphery of the rubber chips at least in an upper layer part of the rubber chip layer.

A drainage ditch 1 is formed, and a bedrock layer 4 is formed on the ground surface 3 where a drainage pipe 2 is buried in the drainage ditch 1. A roadbed layer 5 is formed on a bedrock layer 4, and a cushion layer 6 is formed on the bedrock layer 5. Nonwoven fabric 7 for work is laid over the inside and outside whole surface of a drainage ditch 1 on the ground surface between the ground surface 3 and the bedrock layer 4. The roadbed layer 5 is composed of a roadbed having rubber chips 8 or the like. Rubber asphalt by adding rubber to asphalt is used, or resin asphalt by adding thermoplastic resin to asphalt is used as a pressure sensitive adhesive 10.