Abstract: The present invention relates to a drive unit of a drilling machine, a drive with at least two drive wheels being provided in a drive housing and at least one endless drive being guided around the drive wheels. To improve a drive unit of this type in such a manner that, while having a structure that is as simple as possible, it operates in a functionally reliable way and requires little space, the drive housing in the area of at least one of the drive wheels comprises at least one bay-like bulge which extends over a circumferential section of the drive wheel near the drive wheel.