An agricultural work assistance system includes an input to input agricultural field information about a contour of an agricultural field, dimension information of an agricultural machine or a working device coupled to the agricultural machine, and a work condition about agricultural work on the agricultural field by the agricultural machine and the working device, a route creator to create a traveling route along which the agricultural machine travels within a map of the agricultural field based on the agricultural field information, the dimension information, and the work condition and to secure a turning space where the agricultural machine turns, a turning margin calculator to calculate a turning margin, i.e., a size of the turning space, and determine that the turning margin is insufficient when the turning margin is less than a threshold, and a notifier to provide notification of a place where the insufficient turning margin determined by the turning margin calculator exists.