Plate heat exchanger and heat pump outdoor unit

A plate heat exchanger comprising:

• a first heat transfer plate group configured to exchange heat between a first fluid of high-temperature, high-pressure gas refrigerant and a second fluid of a heating target fluid;
• and
• a second heat transfer plate group configured to exchange heat between a first fluid of low-temperature, high-pressure liquid refrigerant and a third fluid of low-temperature, low-pressure two-phase liquid refrigerant, wherein
• the first heat transfer plate group forms a plurality of refrigerant channels constituted by a stack of plates, has a configuration that a flow of the first fluid of high-temperature, high-pressure gas refrigerant and a flow of the second fluid are alternately aligned in the plurality of refrigerant channels, and causes the second fluid to flow in an outermost one of the plurality of refrigerant channels, and
• the second heat transfer plate group forms a plurality of refrigerant channels constituted by a stack of plates, has a configuration that a flow of the first fluid of low-temperature, high-pressure liquid refrigerant and a flow of the third fluid are alternately aligned in the plurality of refrigerant channels, and causes the first fluid of low-temperature, high-pressure liquid refrigerant to flow in one of the plurality of refrigerant channels adjacent to the first heat transfer plate group.