A device for preventing mobile phone loss for reducing the times of erroneous occurrences of an alarm, and to a method for providing an alarm for mobile phone loss prevention are disclosed. A device for preventing mobile phone loss according to an embodiment of the inventive concept includes a receiving unit that receives a predetermined signal from a pre-registered tag, a calculating unit that calculates a distance between a mobile phone and the tag based on the received signal, a controller that determines whether the mobile phone is in a predetermined safe place, and an alarm providing unit that provides an alarm for preventing the mobile phone loss based on whether the mobile phone is in the safe place and whether the calculated distance is equal to or greater than a predetermined reference distance.