To provide a maintenance method or the like for a functional liquid feeding device capable of detecting whether or not liquid leakage is generated on a functional liquid flow passage from a functional liquid tank to an ink jet head.

The method is the maintenance method of the functional liquid feeding device 23 for pressurizing/feeding the functional liquid to a functional liquid drop delivery head 41 for delivering the functional liquid drop from the functional liquid tank 81 by pressurizing the functional liquid tank 81 by a functional liquid tank 112 and is provided with a liquid leakage detection step for detecting whether or not the leakage of the functional liquid is generated on the functional liquid flow passage from the functional liquid tank 112 to the functional liquid drop delivery head 41; and a liquid leakage informing step for informing the operator of the liquid leakage when the liquid leakage is detected.