To provide an evaporator capable of further improving cooling efficiency of a heating element.

A flat hollow body 4 for taking in and out a refrigerant, having a bulging refrigerant introducing section 32 communicated with a refrigerant inlet and a bulging refrigerant discharging section 33 communicated with a refrigerant outlet is disposed outside of a flat hollow body 2A for circulating the refrigerant, disposed at one end of the evaporator 1. The flat hollow body 4 for taking in and out the refrigerant is provided with a refrigerant introduction opening 34 communicated with the refrigerant introducing section 32 and a refrigerant discharge opening 35 communicated with the refrigerant discharging section 33. The refrigerant flowing into the refrigerant introducing section 32 from the refrigerant introduction opening 34 enters into a refrigerant inlet header section 6 through the refrigerant inlet, the refrigerant from the refrigerant outlet of a refrigerant outlet header section 9 flows into the refrigerant discharging section 33, and is discharged from the refrigerant discharge opening 35. A heat sink 43 for cooling the heating element, on which the heating element is mounted, is brazed along an outer face of the refrigerant discharging section 33 of the flat hollow body 4 for taking in and out the refrigerant.