A refrigerator comprising: a body having at least one storage space for low temperature storage; a compressor in the body for compressing refrigerant; an evaporator for making heat exchange between the refrigerant from the compressor and air in the storage space, the evaporator comprising a refrigerant tube having sections which are arranged horizontally and a plurality of fins arranged in a vertical direction in contact with the refrigerant tube; a frost removal heater for removing frost from the evaporator; an optical sensor having a light emitting unit for directing a light to the evaporator and a light receiving unit for receiving the light from the light emitting unit; a bracket which connects the optical sensor to the evaporator; and a control unit for controlling operation of the frost removal heater with reference to a quantity of the light received at the light receiving unit, wherein the bracket comprises: a body which extends in a vertical direction of the evaporator and has a plurality of slots in which the refrigerant tube of the evaporator is positioned, wherein the plurality of slots are spaced apart in a vertical direction and receive different sections of the refrigerant tube that are separated from one another in the vertical direction, and each slot has a side opening and has elasticity and the plurality of slots are detachably mounted to the refrigerant tube, and a mounting portion, that is bent inward from one end or both ends of the body, to which the light emitting unit and the light receiving unit are mounted in an orientation in which the optical sensor faces the evaporator, the mounting portion being disposed in such a way that distance (d) from the optical sensor to the evaporator is fixedly maintained. a body having at least one storage space for low temperature storage; a compressor in the body for compressing refrigerant; an evaporator for making heat exchange between the refrigerant from the compressor and air in the storage space, the evaporator comprising a refrigerant tube having sections which are arranged horizontally and a plurality of fins arranged in a vertical direction in contact with the refrigerant tube; a frost removal heater for removing frost from the evaporator; an optical sensor having a light emitting unit for directing a light to the evaporator and a light receiving unit for receiving the light from the light emitting unit; a bracket which connects the optical sensor to the evaporator; and a control unit for controlling operation of the frost removal heater with reference to a quantity of the light received at the light receiving unit, wherein the bracket comprises: a body which extends in a vertical direction of the evaporator and has a plurality of slots in which the refrigerant tube of the evaporator is positioned, wherein the plurality of slots are spaced apart in a vertical direction and receive different sections of the refrigerant tube that are separated from one another in the vertical direction, and each slot has a side opening and has elasticity and the plurality of slots are detachably mounted to the refrigerant tube, and a mounting portion, that is bent inward from one end or both ends of the body, to which the light emitting unit and the light receiving unit are mounted in an orientation in which the optical sensor faces the evaporator, the mounting portion being disposed in such a way that distance (d) from the optical sensor to the evaporator is fixedly maintained. a body which extends in a vertical direction of the evaporator and has a plurality of slots in which the refrigerant tube of the evaporator is positioned, wherein the plurality of slots are spaced apart in a vertical direction and receive different sections of the refrigerant tube that are separated from one another in the vertical direction, and each slot has a side opening and has elasticity and the plurality of slots are detachably mounted to the refrigerant tube, and a mounting portion, that is bent inward from one end or both ends of the body, to which the light emitting unit and the light receiving unit are mounted in an orientation in which the optical sensor faces the evaporator, the mounting portion being disposed in such a way that distance (d) from the optical sensor to the evaporator is fixedly maintained.