Abstract: A transaction mediation device stores transaction request information indicating estimates of profit and loss obtained by the first participant through the transaction; transaction provision information indicating estimates of profit and loss incurred based on a thing that the second participant obtains through the transaction; and behavior characteristic information indicating evaluation of behavior characteristics that affect the profit and loss of a transaction counterparty, and, for each of the one or more second participants, calculates, based on the transaction request information and the behavior characteristic information, a first expected profit that the first participant obtains through the transaction with the second participant and a second expected profit that the second participant obtains through the transaction with the first participant; and calculates and outputs a gross profit incurred from the transaction based on the first expected profit and the second expected profit.