To provide a padding method of a sleeper capable of quickly padding a hole by using a urethane resin even when water pools in the hole.

In this padding method of the sleeper, a liquid urethane resin composition is filled in an unrequired hole bored in the sleeper and hindering driving of a rail fixing screw spike, the hole is padded by reacting and hardening the urethane resin composition in the hole, and the screw spike can be driven in a padding part. A water absorptive high polymer is put in the bottom of the hole, and the urethane resin composition is filled in the hole in a state of absorbing moisture in the hole in the water absorptive high polymer.