The purpose of the present invention is to provide a working machine with improved fuel property determination accuracy and a working machine monitoring system using the same. This working machine is equipped with: an engine operation parameter acquisition part (1041) for acquiring engine operation parameters which indicate an operation of an engine mounted on a working machine; a fueling time acquisition part (1011) for acquiring a fueling time at which fuel is supplied to the working machine; and a fuel property determination part (1014) for determining a fuel property on the basis of a comparison result between a time of change in the engine operation parameters and the fueling time.