A maintenance system of a hydraulic excavator (11) is provided with a maintenance monitoring device (21), a maintenance management server (12) for managing trouble information and operating information for each working machine, a model information server (13), and a service personnel mobile terminal (14) connected to one another through the Internet (15). When trouble occurs in the hydraulic excavator, the maintenance system (21) transmits trouble information to the maintenance management server (12), and the maintenance management server (12) transmits information on occurrence of trouble to the mobile terminal (14) and displays it on a display unit. This system manages the maintenance manuals and other data for each model in a model information database separate from the maintenance database and correlates the two databases based on the model data.