A slip determination system is provided that is capable of providing appropriate control information to a traveling vehicle when the traveling vehicle has proceeded to an area where a slip is likely to occur during automatic travel. The slip determination system includes: a vehicle position detection module for detecting a vehicle position； and an automatic travel control portion for enabling automatic travel based on the vehicle position and a set travel path； a slip amount calculation portion for calculating a slip amount of the traveling vehicle body, using an estimated movement distance of the traveling vehicle body calculated based on the number of revolutions of a driving axle of the traveling vehicle body, and an actual movement distance of the traveling vehicle body calculated based on the vehicle position； an appropriateness determination portion for performing appropriateness determination to determine, based on the slip amount, whether or not a state of a traveling ground surface is appropriate for automatic travel； and an automatic travel stop portion for stopping automatic travel based on a determination result.
