A management server for a working machine, including: a reception unit that receives a sensor output from a working machine; a regular report creation unit that creates, for each predetermined period of time, a regular report indicating an operation state of the working machine within the predetermined period of time based on the sensor output; an emergency report creation unit that creates at least one emergency report upon detecting abnormality data representing abnormality of the working machine based on the sensor output; an important report creation unit that creates an important report upon detecting predictive data indicating a sign of the abnormality based on the sensor output; and a delivery unit that delivers the regular report, the at least one emergency report, and the important report, respectively, to a regular report delivery target, an emergency report delivery target, and an important report delivery target.