Disclosed is an evaporator, comprising: a heating tube left as an empty space between first and second case sheets, which form an evaporator case, so as not to be overlapped with a cooling tube, and forming a heating passage in which a working liquid for defrosting flows; and a heater attached to the outer surface, which corresponds to the heating tube, of the evaporator case so as to heat the working liquid inside the heating tube. The heating tube can have a structure which an inlet and an outlet are respectively formed at both sides of a heater attachment part in the longitudinal direction and both end portions of a passage part are respectively connected to the inlet and the outlet, or can have a structure in which an opening is formed at one side of the heater attachment part, the working liquid heated by the heater is discharged through the opening, and the cooled working liquid is returned. The structures can form the heating passage, enabling the working liquid to circulate therethrough, without forming the inlet and the outlet, which are respectively connected to both end portions of the passage part, to be parallel at one side of the heater attachment part.