In a refrigerant evaporator, a first refrigerant collector defined in a tank portion of a first evaporation unit is connected to a second refrigerant distributor defined in a tank portion of a second evaporation unit, and a second refrigerant collector defined in the tank portion of the first evaporation unit is connected to a first refrigerant distributor defined in the tank portion of the second evaporation unit. The refrigerant evaporator includes a connection channel to connect a first refrigerant channel that introduces refrigerant from a heat-exchange core portion of the first evaporation unit to a heat-exchange core portion of the second evaporation unit and a second refrigerant channel that introduces refrigerant from a heat-exchange core portion of the second evaporation unit to a heat-exchange core portion of the first evaporation unit.