An apparatus, for a mobile object, that determines a bid-offer condition on an electricity transaction market: determines an optimal condition making the largest gain for the mobile object from an electricity transaction, on which a contract is executed for electricity that the mobile object directly supplies to an electricity demander, based on an upper limit of an offer electricity amount of the mobile object and a predicted value of a buy price of the electricity demander for an electricity amount, the upper limit determined based on a predicted value of an electricity amount demanded by the electricity demander in each time period and an electricity amount transferable from the mobile object; and determines, as the bid-offer condition, to place an offer on an electricity transaction market at a sell price for a to-be-discharged electricity amount that are determined for each time period in the optimal condition.