A camshaft adjusting device for an internal combustion engine is provided. A functionally reliable camshaft adjusting device designed for a long-lasting operation is obtained when the camshaft adjuster (13) has a lifelong lubrication located in the housing (28, 36, 37) sealed from the surrounding area be sealing covers (36, 37). The camshaft adjuster is not required to be mounted inside the cylinder head (33), but can be mounted as a separate unit on the cylinder head (33) of the internal combustion engine independent of the lubricating oil circuit. This expands, in particular, the range of possibilities for use of the camshaft adjuster (13) with a belt drive.