To provide an evaporator that is simple in piping and in the mounting structure of an expansion valve.

A space between an inlet side tank 2 that collects refrigerant flow passages and receives a refrigerant from the expansion valve 1 and an outlet side tank 3 that collects the refrigerant flow passages on a refrigerant outlet side is integrally provided with a shallow valve case 4 in an outwardly expanded form. The structure of a part mounted with the expansion valve 1 can be remarkably simplified. The valve case 4 facilitates the mounting of the expansion valve 1 by virtue of the outwardly expanded form, and can dispense with piping between the expansion valve 1 and the evaporator to improve assembly performance by virtue of the integral structure.