The invention discloses a soaking sterilization device. The soaking sterilization device comprises a sterilization box, wherein the sterilization box comprises a box body with an inner cavity, and a box cover rotatably arranged on the box body in an opening or closing way; a first sterilization case capable of being accommodated in the inner cavity of the box body is suspended on the box cover; and a plurality of first liquid flow through holes are formed at the bottom of the first sterilization case. When instruments are sterilized by using the sterilization device, the instruments are classified first according to the specific gravity of the instruments to be sterilized, the instruments having the specific gravity greater than that of a disinfectant are placed in the first sterilization case, the instruments having the specific gravity smaller than that of the disinfectant are placed in the box body, the first sterilization case is accommodated in the inner cavity of the box body when the box cover is closed and the instruments with smaller specific gravity in the inner cavity of the box body are pressed into the disinfectant, so that the instruments with smaller specific gravity are completely soaked in the disinfectant so as to be effectively sterilized. The soaking sterilization device is simple in structure, convenient to use and low in production cost.