A refrigerator using a non-azeotropic refrigerant mixture (NARM) and a control method thereof. The refrigerator reduces the rotational speed of a freezing chamber fan or stopping the freezing chamber fan for a designated time, and/or increasing the rotational speed of a compressor in a simultaneous freezing/refrigerating operation mode of an NARM cycle as compared to a freezing operation mode, and may thus decrease evaporation latent heat of a refrigerant consumed by a freezing chamber evaporator and relatively increase evaporation latent heat of the refrigerant usable in a refrigerating chamber evaporator without increase in a charging amount of the refrigerant, thereby preventing over-charging due to increase in the charging amount of the refrigerant and reducing cycling loss.