The invention is directed to a machine tool for laser beam machining of workpieces, comprising a housing mounted on a column and having a longitudinally movable guide tube disposed therein. The rear end portion of the housing has a laser unit mounted thereon, and the laser beam passes through a focussing optical system and exits from a nozzle head provided with means for supplying at least one fluid to the central exit opening of the laser beam. In order also to enable metal cutting machining of a workpiece the invention provides for a motor driven hollow main spindle journaled within the housing, the spindle having locking elements for fixing a tool holder therein. Advantageously, the focussing optical system and the nozzle head are attached to a standardized tool holder which can be fitted into the main spindle.