To calculate the maximum value or the minimum value in the same constitution and in the same processing, for example, at the time of electronic competitive bidding.

A bidding device and a ballot-counting device 12 are respectively provided with an conversion table 21 for index values (k) 1, 2,..., N and corresponding values (Pk) P1, P2,..., PN, and a participant J calculates an index value iJ corresponding to a bid value PiJ, and calculates a value hN+1 (IVJ) and g (hij (IVJ)) multi-hashed with an initial value IVJ of J, and transmits them to the ballot-counting device 12. When all the participants finish registration, the device 12 transmits an inquiry about whether or not the registration is executed successively from N to all the participant, and each participant returns hm (IVJ) corresponding to the index value (m). A the time of receiving a value matched with the registered g (hij (IVJ)), the (m) at that time is defined as the highest index value among the registered values, and the registered value is clarified. In the table 21, when P1<...<PN are obtained for the indexes 1,..., N, the maximum bit value is calculated, and when P1>...>PN are obtained for 1,..., N, the minimum bit value is calculated.