A plurality of boring cutters and honing stones are coaxially arranged on a machining head. A bar member is reciprocatingly inserted and splined within a rotary hollow spindle. Both the end opening surface of the spindle and the end of the bar member are taper-engaged with each other so that the bar member may be disengaged and moved forwardly with respect to the spindle. The machining head is coupled with the end surface of the bar member. When the spindle is taper-engaged with the bar member, a workpiece is bored. When the bar member is moved forwardly to release the taper engagement, the workpiece is honed by reciprocating the bar member and the machining head. Thus, the honing operation can be performed with a rigid structure, and both boring and honing operations can be effected by the same machining head.