The invention discloses an arsenic alkali slag resource utilization device. The device comprises an electric reduction furnace, a powder air lock meter feeding device, an ammonia spraying device, a heat exchanger, a residual ammonia collating device, a centrifugal fan and an ammonia storage device. An arsenic alkali slag resource utilization method comprises the following steps that preheated arsenic alkali slag powder materials are fed into the electric reduction furnace, the ammonia is directly sprayed into the material in the furnace to be subjected to the reduction reaction, elemental antimony obtained through the reduction reaction is discharged out of a bottom outlet of the reduction furnace, rough antimony is obtained, residue is discharged out of a residue discharging opening of the side of the reduction furnace, alkali slag is obtained, elementary arsenic steam obtained through spraying reduction sublimation enters a cooler to be condensed and solidified along with hot waste airflow pulled out of an induced draft fan, rough arsenic is obtained, waste gas enters the residual ammonia collating device for waste ammonia collecting and circular use, the process flow is simple,automatic control is easy, investment is small, the treatment amount is good, the device is safe and environment friendly, the arsenic alkali slag is treated and separated thoroughly, and the arsenicalkali slag difficultly treated well serves as a raw material for producing arsenic, antimony and alkali.