The invention discloses a soil compacting device. The soil compacting device comprises a basic framework, a driving device, a transmission component and an execution component, wherein the driving device and the transmission component are arranged on the basic framework; the execution component is arranged on the transmission component; power of a vibrating motor is delivered to a shaft coupling through a speed reducer to drive a cam shaft to rotate; a cam intermission mechanism is used for converting cam shaft rotational motion into upward-downward reciprocating motion along a vertical direction in order that a soil sample box vibrates up and down intermittently; the soil sample box is separated from the cam intermission mechanism after moving to a highest point, and comes into contact with the top of the cam intermission mechanism through free falling in order that soil in the soil sample box is compacted; the soil is compacted gradually by a plurality of cycles. The mass and bulk weight of the soil in the soil sample box are calculated according to the total mass and remaining mass of soil added into a feeding bucket, and the vibration time is adjusted to obtain soil of different bulk weights needed by tests. By adopting the soil compacting device, preparation of large-bulk-weight soil can be realized, and the soil particle diameter distribution range is widened.