The present invention provides a maintenance system, which centrally performs a management operation on the life expectancies of expendable components of machine tools (21) provided in a plant for systematic maintenance of the machine tools (21). The maintenance system comprises a plurality of machine tools (21) and a management unit (20) connected to the machine tools (21). The management unit (20) comprises: a life expectancy determining section (92) for determining the degrees of wear of driver mechanisms on the basis of data indicative of the operating conditions of the driver mechanisms received from a controller (80) provided in each of the machine tools (21); a data storage section (91) for storing data indicative of the wear degrees determined by the life expectancy determining section (92), and an output section (93,95) for outputting information on the wear degrees stored in the data storage section (91). The wear degrees of the respective driver mechanisms are centrally managed, so that a comprehensive maintenance plan can easily be formulated for the machine tools (21).