EVAPORATOR

An evaporator includes: a cylindrical member 10 through which a heating medium can flow; a heat exchange structure provided on a radially inner side of the cylindrical member 10; and a jacket member 30 provided on a radially outer side of the cylindrical member 10 with a space so as to define a flow path for a liquid and a vapor thereof, the jacket member 30 having a feed port 31 for a liquid M1 and a discharge port 32 for a vapor.