To overcome problems there is to be provided useful information to a user, by counting the number of detected RF tags. As a means for solving the problems an information-providing server 20 according to the present invention acquires IDs of RF tag readers disposed near by the Ferris wheel, when there has been presented to the information providing server 20, as a notifying condition, the condition that a user desires to receive an e-mail on the occasion of the number of persons waiting in line for a Ferris wheel having become seven or less. Then after having acquired the number of plural IDs of the RF tags detected by the RF tag readers having the acquired IDs, the information-providing server 20 acquires attribute information of the RF tags. The information providing server 20 counts the number of IDs of RF tags whose attribute is a person, referring to the attribute information. When the counted result has become seven or less, the information providing server 20 transmits an e-mail notifying to the effect that the congestion has been relieved to the mobile terminal 10.