To provide a method for treating a thermit weld zone of a rail which can improve fatigue strength of a thermit weld zone easily and reliably on site and easily confirm the fatigue strength.

Plastic working in excess weld metal toe part 7a on the upper face of the rail bottom in a thermit weld zone 2 of a rail 1 increases hardness, yield strength and tensile strength in the excess plastically worked weld metal toe part 7a as a result of work hardening and, imparts compressive residual stress, resulting in improved fatigue strength of the thermit weld zone. This can easily be confirmed by visually inspecting the plastically worked part.