Abstract: A system of sorting elongated pieces such as asparagus, wherein each of the elongated pieces are successively conveyed by a conveyer and detected as a still image by a sensor such as a TV camera. In processing a signal representative of the still image a stem diameter of the piece and a ratio of the spike maximum diameter of the piece to the stem diameter are obtained as sorting out factors by calculation. When the calculation values of the sorting out factors satisfy predetermined reference values, the piece is further sorted out according to size. The stem diameter is measured at a position which is spaced from the cut end of the stem by a predetermined dimension toward the spike thereof.