Using a single concentrated scheduling system in a large-scale manufacturing system is problematic. As a result, scheduling systems are being introduced in departmental units, which has resulted in having to repeat schedule adjustments between departments whenever there is a change in one department. Therefore, the authors propose a horizontal distributed scheduling system to create speed and localization in schedule adjustments which occur frequently between departments by introducing a multiagent model to perform negotiations between schedulers by using each departments scheduler as an agent. The negotiations between schedulers in this system are characterized by defining the negotiation protocol which controls the flow of the negotiations so as to maintain consistency between schedulers and by introducing a mechanism to enable simultaneous execution of multiple negotiations so as to create speed in schedule adjustments. In addition, the authors evaluated the application of this system to scheduling problems in a real multiple work job shop. They confirmed that speed was achieved through simultaneous implementation of multiple negotiations while at the same time consistency in schedules was maintained via negotiations between schedulers.