An automatic conveying device and a maintenance method therefor. The automatic conveying device includes a fixed step drive wheel, and a step driven wheel located on a movable bracket; a step chain in transmission connection with the step drive wheel and the step driven wheel; a tensioning device that acts on the movable bracket to maintain the step chain in tension; a sensor device that detects a displacement of the movable bracket; and a processor configured to send a first warning signal when a single-trip displacement of the movable bracket exceeds a first threshold, and to send a second warning signal when a accumulative displacement of the movable bracket exceeds a second threshold.