Abstract: A motion base device for simulators is disclosed. In the motion base device, an upper plate is positioned above a base plate with a simulating cabin being carried on the upper plate. Three cylinder actuators are positioned between the base and upper plates so as to heave, pitch and/or roll the upper plate relative to the base plate. Of the three cylinder actuators being respectively placed at apexes of a regular triangle, the first one is fixedly mounted to the base plate and is jointed to the upper plate using a universal joint. Each of the second and third cylinder actuators is jointed to the base and upper plates using a universal joint and a joint block. A hydraulic pressure supply unit supplies pressurized oil to the three cylinder actuators so as to allow the three cylinder actuators to be independently operated.