A refrigerant evaporator includes an upstream tank portion for distributing refrigerant into all laminated tubes of a core portion. The upstream tank portion includes a first distribution passage for distributing the refrigerant into the tubes in a direction parallel to a tank longitudinal direction, a second distribution passage for distributing the refrigerant from the first distribution passage into the tubes in a tank width direction, and a communication passage through which the refrigerant from the first distribution passage is supplied to the second distribution passage after flowing in the tank longitudinal direction.