PURPOSE: To simply perform flushing work in a maintenance device for a fluid- actuated device.

CONSTITUTION: A maintenance device is provided with a fluid-actuated device actuated by working fluid, actuation adjusting mechanism 42 and 44 to adjust an actuating condition of the fluid-actuated device and a control means 60 to control the actuation adjusting mechanisms 42 and 44, and is provided with a maintenance device 7 to diagnose failure of respective parts of the fluid- actuated device as well as to command maintenance operation and a flushing device 6 to remove impurity in the working fluid, and a flushing mode to command so as to assist cleaning in a fluid circuit at actuating time of the flushing device 6 is provided in the maintenance device 7.