A heat exchanger for operating in a cooling operation mode for cooling a region to be heat-exchanged or in a drying operation mode for receiving wind supplied from a blowing fan, the heat exchanger comprising: a refrigerant pipe defining a flow path of a refrigerant; a cooling fin coupled to the refrigerant pipe; and a hydrophilic coating coated on a surface of at least one of the refrigerant pipe and the cooling fin , wherein the hydrophilic coating contains : a first type transition metal oxide that becomes acidic by catalytic reaction with moisture formed on the refrigerant pipe or the cooling fin to have antimicrobial activity when the heat exchanger is operated in the cooling operation mode; and a second type transition metal oxide or a post-transition metal oxide that has antimicrobial activity by photocatalytic reaction when the heat exchanger is operated in the drying operation mode, characterised in that a total content of the first type transition metal oxide and the second type transition metal oxide or a total content of the first type transition metal oxide and the post-transition metal oxide is 2 to 10 wt.% of the hydrophilic coating , wherein the first type transition metal oxide exhibits weak acidity by the catalytic reaction with moisture formed on the refrigerant pipe or the cooling fin, and wherein a pH value of the weak acidity is in a range of pH 5 to pH 6. a refrigerant pipe defining a flow path of a refrigerant; a cooling fin coupled to the refrigerant pipe; and a hydrophilic coating coated on a surface of at least one of the refrigerant pipe and the cooling fin , wherein the hydrophilic coating contains : a first type transition metal oxide that becomes acidic by catalytic reaction with moisture formed on the refrigerant pipe or the cooling fin to have antimicrobial activity when the heat exchanger is operated in the cooling operation mode; and a second type transition metal oxide or a post-transition metal oxide that has antimicrobial activity by photocatalytic reaction when the heat exchanger is operated in the drying operation mode, characterised in that a first type transition metal oxide that becomes acidic by catalytic reaction with moisture formed on the refrigerant pipe or the cooling fin to have antimicrobial activity when the heat exchanger is operated in the cooling operation mode; and a second type transition metal oxide or a post-transition metal oxide that has antimicrobial activity by photocatalytic reaction when the heat exchanger is operated in the drying operation mode, characterised in that a total content of the first type transition metal oxide and the second type transition metal oxide or a total content of the first type transition metal oxide and the post-transition metal oxide is 2 to 10 wt.% of the hydrophilic coating , wherein the first type transition metal oxide exhibits weak acidity by the catalytic reaction with moisture formed on the refrigerant pipe or the cooling fin, and wherein a pH value of the weak acidity is in a range of pH 5 to pH 6. wherein the first type transition metal oxide exhibits weak acidity by the catalytic reaction with moisture formed on the refrigerant pipe or the cooling fin, and wherein a pH value of the weak acidity is in a range of pH 5 to pH 6. <EOS>