This paper describes the horizontal machining center with turning function. In the past, when machining parts such as valve and pump, the turning process was essential for machining of a large-diameter seat surface and an inclined surface. Now, machining of such surfaces can be taken over to the single horizontal machining center, thanks to the development of a new machining center (NX76B) and ORBIT BORING function (i. e., turning function). The most outstanding features of this horizontal machining center are summarized as 1) machining of various diameters with same tool, 2) realization of facing operation without U-axis control function, and 3) realization of both turning operation and operation of a horizontal machining center by the single machine.