An apparatus for forging a hollow body from a pre-perforated hollow block includes forging tools that can be driven radially in relation to a forging axis, a clamping head which is displaceable on a guide bed in the direction of the forging axis and includes collet chucks for the hollow block, and a mandrel carriage which is arranged on the side of the clamping head facing away from forging tools, which is displaceable independently of the clamping head along the guide bed, and whose mandrel bar provided with the forging mandrel penetrates the clamping head coaxially to the forging axis. In order to provide advantageous constructional conditions the mandrel carriage includes an axial actuating drive for the mandrel bar and can be coupled in a tension-proof manner to the clamping head.