In a maintenance work system for a substrate processing plant including a device space in which a substrate processing system is installed, and a travel space in which a work body involved in maintenance work on the substrate processing system travels, the travel space being located above or below the device space, the maintenance work system includes the work body, and a vertical transfer mechanism configured to move the work body up or down between the travel space and the device space, the work body having travelled to a position above and horizontally proximate to the substrate processing system on which the maintenance work is to be performed or a position below and horizontally proximate to the substrate processing system on which the maintenance work is to be performed.