To measure the grade of ore in an underground mining method.SOLUTION: An underground tunnel is based on a mining plan of a mine planned based on first grade data measured by a preliminary geological survey and first position data corresponding to the first grade data. A measurement system that measures a grade of excavated material produced from the underground tunnel that includes multiple mining points comprises: a measurement unit (grade-measurement unit) 61 that measures the grade of excavated material produced from the underground tunnel, a second grade data acquisition unit (grade-data-acquisition unit) 72 that acquires second grade data indicating the grade of the excavated material from the measurement unit 61, and a second position data acquisition unit (position-data-acquisition unit) 73 for acquiring second position data corresponding to the second grade data.SELECTED DRAWING: Figure 4