PURPOSE: To suppress the meandering of a machine body and improve comfortableness to ride by calculating the extent of regulation by a travel direction regulating means from a variation in distance of a direction sensor body for transverse reaping from the end of an unreaped grain culm group and the travel speed of the combine harvester and controlling the travel direction.

CONSTITUTION: The extent of regulation by a travel direction regulating means according to travel braking of crawlers (21R) and (21L) is calculated from a variation in distance of a direction sensor body for transverse reaping from the end of an unreaped grain culm group and measured values of a travel speed sensor 23. Thereby, hunting can be prevented from occurring.