A periphery monitoring device (10) comprises a monitor (50) that displays a bird's-eye image (200) that includes an image of a dump truck (1), a payload meter ECU (21) that detects the load of the dump truck (1), and a controller (20) that switches the size of a cargo image (C1) displayed over the vessel (4) of the dump truck (1) and displays this image on the monitor (50) on the basis of the detection result of the payload meter ECU (21).In a load display device for a dump truck, a plurality of cameras are installed and the load display device monitors the periphery by using a bird's-eye image that combines images obtained by the plurality of cameras. The load display device includes a display component, a detector and a display controller. The display component is configured to display the bird's-eye image including an image of the dump truck. The detector is configured to detect a load of the dump truck. The display controller is configured to switch a size of a simulated cargo image displayed over a vessel of the dump truck based on a detection result of the detector and to display the simulated cargo image on the display component.