PURPOSE: To realize uniform pushing and squeezing avoiding a microscope nonuniform distribution is pressurizing, by a method wherein a laminated body obtained by superposing a plurality of unfired ceramic sheets upon each other is put on a plane of a backplate, held in a bag comprised of flexible plastic, the inside of the bag is exhausted and decompressed, the bag is held within a fluid and pressure of the fluid is raised.

CONSTITUTION: A laminated body 1 of a prepress-bonded green sheet is put on a backplate 2 of a copper block and the whole is held in a bag 3 made of a plastic film. The inside of the bag 3 is decompressed down to a pressure close to a state by a vacuum device connected with an exhaust port 4. The plastic film is stuck close to the laminated body and the laminated body and backplate also are pressed against each other by atmospheric pressure. A vacuum-packed substance is held into a pressure vessel 5, silicone oil 6 is filled into the vessel 5 by a conduit 7, the conduit 7 is connected with a pressurizing device also and pressure of the silicone oil in the pressure vessel can be raised to 50-300kg/cm2. Static hydraulic pressure of 200kg/cm2 is applied to a treated body while heating the same at, for example, 90°C and hot press bonding treatment is performed. The laminated body is fired within N2 and a multi-layer ceramic board is obtained after that.