There are provided reflow apparatuses and a methods therefor. In some embodiments, a reflow apparatus includes a first heating unit capable of heating a solder on a substrate up to just below before a melting point of the solder at ambient pressure such that the solder on the substrate is melted and electronic components mounted on the substrate are then soldered to the substrate; and a second heating unit connected to the first heating unit, the second heating unit capable of heating the solder on the substrate heated in the first heating unit through at least a portion of a solder melting temperature range in a vacuum state.