Real-Time Bidding (RTB) is such that goods are traded by way of auction on a real-time basis and ad spot has been done in this way in recent years. RTB is thus a new auction style for bidders called Demand-Side Platform (DSP) because the number of trades and bidding styles are different from those in conventional auctions. This study explores an effective and less costly bidding strategy to make more successful bids in RTB by agent-based approach. In the simulation model, auctions of ad spots occur in accordance with time slots in a day and the participants bid based on their strategies. The computational experiments show that staying out is of particular importance.