The invention provides a device for killing the underground pests of konjac. The device comprises a motor, a left shell, a right shell, bearings, spiral cutters, a handle, ultraviolet lamps, a storage battery, rivets, a screw and pins and is characterized in that the left shell and the right shell form a motor shell wrapping the motor and a handle connecting shell wrapping the bottom end of the handle; motor shafts on two sides of the motor extend out of the bearing mounting tube of the left shell and the bearing mounting tube of the right shell, and one bearing sleeves each of the two bearing mounting tubes; one spiral cutter is mounted on each of the left bearing and the right bearing, the inner-side area of the central sleeve of each spiral cutter sleeves the corresponding bearing, and the outer-side area of the central sleeve of each spiral cutter is fixed on the motor on the corresponding side of the motor through one pin; the ultraviolet lamps are mounted on the bottom surfaces of the left shell and the right shell; the storage battery is mounted inside the handle, the motor is started to drive the left spiral cutter and the right spiral cutter to rotate after a switch on the handle is turned on, and the ultraviolet lamps are turned on at the same time. By the device, the underground pests of the konjac can be killed during the weeding and soil loosening of the konjac.