A tourism serious game requires a transaction system to handle the transaction process's visualization between players. In this paper, we propose a serious game with a blockchain-based multiplayer transaction system. To integrate the transaction system with the game engine, we use the ethereum platform. In this serious game, ethereum handles the simulation of transaction activities between several characters' choices, including tourists, ticket sellers, jeep drivers, traders, and horse rental. The experimental results show that the gas price variable affects the speed of the transaction process. Meanwhile, setting the gas limit value in this serious game affects the transaction process's success rate between players.