A cooler configured to cool an electronic device includes: a refrigerant inlet portion configured to guide refrigerant from an outside of a casing to an inside of the casing; a refrigerant outlet portion configured to guide the refrigerant from the inside of the casing to the outside of the casing; and a metal member configured to define a flow path region in which the refrigerant is caused to flow from the refrigerant inlet portion to the refrigerant outlet portion in the inside of the casing. The metal member includes: a plurality of opening portions configured to cause the refrigerant to pass therethrough; and a capture and reduction portion having such a shape as to capture air bubbles, which are generated through a connection surface between the casing and the electronic device, so as to reduce the air bubbles through cooling by the refrigerant when the electronic device is cooled.