The invention relates to an automatic sand filling device, which comprises a platform, a bracket, a sand filling gun, a tilted pipe, a quantitative hopper and a storage bin. A sand filling method using the device comprises the following steps that: a craneman lifts a ladle to a sand filling position; the craneman sends a sand filling signal; the device finishes sand filling automatically; the device sends a sand filling complete signal to the craneman; and the craneman lifts the ladle away. The device and the method have the advantages of reducing the consumption of ladle filler sand and the labor intensity of workers, and the device and the method are perfect.