This invention is to provide a technique enabling to efficiently collect effectiveness information as to evaluation information for evaluation objects, with reliability. An informant tourist A registers recommendation information of a tourist resort to an information broker C. The information broker C opens registered evaluation information to the public through the Internet. An information utilizing tourist B accesses to a web site of the information broker C and looks for his or her favorite store. The information utilizing tourist B finds evaluation information registered by the informant tourist A and goes to a tourist resort store D of its evaluation object. The information utilizing tourist B negotiates a deal about benefits with the tourist resort store D. If the negotiation is concluded, the deal is concluded, and then, the information utilizing tourist B causes a display device of a cellular phone to display a screen for inputting a password of the tourist resort store D and prompts to input its password. The tourist resort store D inputs and sends its password to the information broker C. This is not only a proof that the deal was concluded but also that a convincing proof that the deal was concluded based on the evaluation information of the informant tourist A. Namely, it is a proof that the evaluation information of the informant tourist A is reliable and was utilized effectively. If the deal is concluded, the tourist resort store D pays a commission to the information broker C. The information broker C gives points to the informant tourist A and the information utilizing tourist B.