Provided is a tractor which allows continuation of a plowing work by appropriately elevating a plow when slip occurs in wheels. The tractor includes draft controlling means (34) for elevating the plow to a target machine body level value obtained by making reference to control information with a draft load value detected by a draft load sensor (S). The control information is set based on a target plowing depth set when the plow was set to a target plowing depth and a draft load value. When a slip ratio detected by a slip ratio acquiring means (37) exceeds a threshold value, in place of previously set control information, there is newly set control information which renders higher the target machine body level relative to a same draft load value, thereby to elevate the plow.