The invention discloses a parallel flow heat exchanger. The parallel flow heat exchanger comprises a parallel flow heat exchange module; the parallel flow heat exchange module comprises a first flow collecting pipe, a second flow collecting pipe and multiple refrigerant pipes; the refrigerant pipes are horizontally arranged between the first flow collecting pipe and the second flow collecting pipe; heat dissipating pieces are arranged between two adjacent refrigerant pipes, and are provided with water drainage holes; at least one first partition is arranged in the first flow collecting pipe for dividing the first flow collecting pipe into multiple first refrigerant cavities; at least one second partition is arranged in the second flow collecting pipe for dividing the second flow collecting pipe into multiple second refrigerant cavities; projections of the first partitions and the second partitions on a vertical surface are alternated; and the refrigerant pipes communicate with the corresponding first and second refrigerant cavities. The improvement of the user experiences and the heat exchange efficiency of the parallel flow heat exchanger is realized.