To provide a reflow furnace and a method of cooling components in the reflow furnace reducing temperature unevenness of a board by evenly cooling non-heat-resistant components mounted on the board and requiring no removing work of flux.

The reflow furnace 1 for heating the non-heat-resistant components 101 to 104 to electrically connect them to a board P with solder 300 while transferring the board P, on which the non-heat-resistant components 101 to 104 are mounted comprises a cooling section 60 for cooling the non-heat- resistant components 101 to 104 on the board P when heating the board P by transferring it after preheating it; and the cooling section 60 comprises an air spraying section 70 for spraying air curtain for cooling to the board P along the direction of the board P separated by at some intervals, and an exhausting section 80 for taking in and exhausting the air curtain AK for cooling sprayed from the air spraying section 70.