An apparatus for defrosting an evaporator in a refrigeration system using an infrared emitting diode includes i) a frost detection sensor configured to receive a frost sensing signal from an output part of a control processor and to transmit a frost detection signal into an input part of a control processor, wherein the frost detection signal is generated by projecting infrared to the frost and receiving reflection-infrared from the frost; ii) a control processor configured to convert the frost detection signal into a digital signal in the signal converting part, to evaluate if the frost detection signal is higher than a threshold value which is set from a signal setting part, and to transmit the operation signal to the defroster, as well as the display signal to the signal display part; and iii) a defroster.