A heat pump system includes a first heat pump and a second heat pump. The first heat pump includes a first outdoor unit. The first outdoor unit includes a compressor, an outdoor-unit connecting pipe, and a refrigerant filling port. The outdoor-unit connecting pipe connects an intake path of the compressor and a second outdoor unit of the second heat pump for supplying a refrigerant to the second outdoor unit of the second heat pump. The refrigerant filling port is provided in a portion of the outdoor-unit connecting pipe.