A heat exchanger includes first and second headers connected to end portions of heat transfer tubes. The second header includes a header pipe defining a flow space that communicates with the heat transfer tubes and, when the heat exchanger acts as an evaporator, allows refrigerant in a two-phase gas-liquid state to pass through the flow space into the heat transfer tubes. A bypass pipe is disposed between an entrance portion and the first header. The entrance portion has an entrance distance L between a connection end portion connected to a refrigerant pipe and a central axis of the bypass pipe. The entrance distance L of the entrance portion satisfies L≥5di, where di is an inner diameter of a flow space of the header pipe on an orthogonal plane orthogonal to a direction of refrigerant flow. The bypass pipe is inserted in the flow space of the entrance portion.