PURPOSE: To improve classification efficiency by automatically selecting an appropriate classification axis by finding the evaluation value of the item value of an item sampled from a retrieval result and providing by classifying the retrieval result to a retriever based on a selected classification axis.

CONSTITUTION: This sorter is equipped with an item/item value sampling means 3 which samples the item 31 and the item value 32 from the retrieval result 1, a classification axis selecting means 4 which selects the classification axis from sampled item 31 and item value 32, and a classification execution means 5 which classifies the retrieval result 1 based on the selected classification axis.