The invention provides a gas-liquid separating pipe for a heat exchanger and the heat exchanger. The gas-liquid separating pipe comprises a main body section and at least one open area variation section (63). The main body section comprises a top inlet and a bottom outlet, a refrigerant inlet channel (61) and an air guiding channel (62) are separately arranged at the inlet, the open area variation sections (63) are located below the inlet, and the open area of each open area variation section (63) is smaller than that of the main body section. By means of the technical scheme, the problems that in the prior art, gas-phase refrigerants and liquid-phase refrigerants in a heat exchanger are not uniform in distribution and the heat exchange performance is poor can be effectively solved.