The present invention pertains to a combined machining equipment for steel tubes, and a machining method is of a small size, can easily be moved, and is capable of not only flaring a steel tube, but also grinding a flared surface, forming a groove, and peeling off a lining. A main shaft (121) is rotatably mounted on a slide frame (141) slidable with respect to a common mount (103), and a second machining head (124) is mounted on a flange on the distal end of the main shaft (121). An auxiliary shaft (131) is slidably disposed in the main shaft (121) for rotation therewith. A first machining head (134) is mounted on a mount base (132) on the distal end of the auxiliary shaft (131). When the main shaft (121) is rotated and moved back and forth and the auxiliary shaft (131) is moved back and forth with respect to the main shaft (121), the first machining head (134) spreads the tip end of a steel tube (110) held by a steel tube holding apparatus (102) to a first position, and the second machining head (124) spreads the tip end of the steel tube (110) to a predetermined flanged position, thus flaring the tip end of the steel tube (110).