To provide a hydroforming apparatus and a hydroforming method, by which apparatus and method, a product having excellent sealing property can be manufactured by deep drawing without welding all of peripheral portions of two or more metallic plates.

The hydroforming apparatus is used to bulge two or more metallic plates, and is used as "a first working apparatus" having sliding seals arranged on plate holding surfaces to be brought into contact with one or both of the metallic plates and non-sliding seals arranged on the plate holding surface to be brought into contact with the other of the metallic plates or is used as "a second working apparatus" having the sliding seals arranged on the plate holding surface to be brought into contact with the uppermost surface and the lowermost surface of the metallic plates and metallic die seals arranged on the portions separated from the plate holding surface. In addition, in the hydroforming method, two or more metallic plates are used as raw materials, and the bulging work is carried out by supplying working fluid between the metallic plates.