An integral casting flask/vacuum chamber combination is disclosed in which an inner tube forming the casting flask is disposed coaxially inside of an outer tube thus forming a vacuum chamber between the two tubes. The inner tube has holes formed in its circumference to provide for uniform evacuation of air from the investment for pulling the casting material into the mold. A shoulder portion integrally connects the inner tube with the outer tube in such a way that the bottom edge of the inner tube is suspended above the bottom edge of the outer tube and the top edge of the inner tube is suspended above the top edge of the outer tube. This device is used in combination with a vacuum table and does not require the complex and expensive conventional vacuum chamber.