A method for operating a clothes treating apparatus comprising: a drum configured to accommodate therein an object to be dried; an air suction means configured to form a flow path of air introduced into the drum; an air exhaustion means configured to form a flow path of air exhausted from the drum; a condenser disposed to heat air sucked into the drum through the air suction means; an evaporator disposed to cool air exhausted from the drum through the air exhaustion means; a compressor configured to compress a refrigerant introduced from the evaporator; and a variable expander configured to expand a refrigerant introduced from the condenser, and having a variable open degree, the method comprising: measuring a temperature (Tei) of a refrigerant introduced into the evaporator, and a temperature (Tci) of a refrigerant introduced into the compressor, and calculating a temperature difference (Tci-Tei) between the two measured temperatures; characterized by comparing the temperature difference (Tci-Tei) with a predetermined first value and a predetermined second value, wherein the predetermined second value is larger than the predetermined first value; and changing an open degree of the variable expander based on the comparison result, by: maintaining an open degree of the variable expander if the temperature difference is between the two predetermined values; decreasing the open degree of the variable expander if the temperature difference is less than the predetermined first value; and increasing the open degree of the variable expander if the temperature difference is larger than the predetermined second value, wherein in the step of changing the open degree of the variable expander, an open degree change width is determined based on a current open degree of the variable expander. a drum configured to accommodate therein an object to be dried; an air suction means configured to form a flow path of air introduced into the drum; an air exhaustion means configured to form a flow path of air exhausted from the drum; a condenser disposed to heat air sucked into the drum through the air suction means; an evaporator disposed to cool air exhausted from the drum through the air exhaustion means; a compressor configured to compress a refrigerant introduced from the evaporator; and a variable expander configured to expand a refrigerant introduced from the condenser, and having a variable open degree, the method comprising: measuring a temperature (Tei) of a refrigerant introduced into the evaporator, and a temperature (Tci) of a refrigerant introduced into the compressor, and calculating a temperature difference (Tci-Tei) between the two measured temperatures; characterized by comparing the temperature difference (Tci-Tei) with a predetermined first value and a predetermined second value, wherein the predetermined second value is larger than the predetermined first value; and changing an open degree of the variable expander based on the comparison result, by: maintaining an open degree of the variable expander if the temperature difference is between the two predetermined values; decreasing the open degree of the variable expander if the temperature difference is less than the predetermined first value; and increasing the open degree of the variable expander if the temperature difference is larger than the predetermined second value, wherein in the step of changing the open degree of the variable expander, an open degree change width is determined based on a current open degree of the variable expander. measuring a temperature (Tei) of a refrigerant introduced into the evaporator, and a temperature (Tci) of a refrigerant introduced into the compressor, and calculating a temperature difference (Tci-Tei) between the two measured temperatures; characterized by comparing the temperature difference (Tci-Tei) with a predetermined first value and a predetermined second value, wherein the predetermined second value is larger than the predetermined first value; and changing an open degree of the variable expander based on the comparison result, by: maintaining an open degree of the variable expander if the temperature difference is between the two predetermined values; decreasing the open degree of the variable expander if the temperature difference is less than the predetermined first value; and increasing the open degree of the variable expander if the temperature difference is larger than the predetermined second value, wherein in the step of changing the open degree of the variable expander, an open degree change width is determined based on a current open degree of the variable expander.