To provide a cab supporting structure capable of supplying a protection function with a simple configuration by using an attenuation mechanism commonly used for a controlled vehicle for protecting the cab or an operator from high impact force acting on the cab while absorbing vibration and shock on the cab in a normal condition when a construction machine falls down. The cab supporting structure is provided with an attenuation mechanism elastically supporting a cab against a frame. A regulation member, only when certain displacement is generated in the cabin the extension direction of the attenuation mechanism, regulating this displacement is provided separately from this attenuation mechanism. The regulation member regulates the displacement of the cab before a stroke end of the attenuation mechanism. Upon arranging a work equipment on the frame, the regulation member is provided at least at the opposite side of the work equipment.