Abstract: A retrieval device 10 includes an input unit 11 configured to receive a search query from a user, a retrieval unit 12 configured to calculate a degree of fitness between the search query and each of a plurality of pieces of retrieval target data, a query expansion unit 13 configured to generate an expanded search query, and a policy determination unit 14 configured to determine which of a first process and a second process is to be executed on the basis of the degree of fitness for each piece of the retrieval data calculated by the retrieval unit 12. The first process is presenting the retrieval target data having a high degree of fitness to the user. The second process is proposing to the user that the retrieval unit is caused to calculate the degree of fitness for each piece of the retrieval target data using the expanded search query.