A left support pillar includes a protective portion extending substantially vertically in front of a back rest of the operator seat so as to cover an operator seat sideways, a fixing portion fixed onto a rotating frame at a position behind the operator seat, and a connecting portion adapted to extend forward from the fixing portion and to be connected to a lower end of the protective portion. The protective portion is disposed within a predetermined range of a seating surface of the operator seat and is formed upward from a position lower than an upper end of the back rest.