An attachment structure for attaching an auxiliary fitting such as a parallel ruler to a portable machining apparatus allows simpler assembly and maintenance. A portable machining apparatus includes a base having a lower surface to be in contact with a workpiece, a machining body supported on an upper surface of the base, and a mount that receives an auxiliary fitting removably attachable to the base. The mount includes an internal threaded fastener detachably supported on the base, an external threaded fastener screwed with the internal threaded fastener to be tightened with the internal threaded fastener to press the auxiliary fitting onto the base, and a locking section that locks the external threaded fastener with respect to the internal threaded fastener.