The invention relates to a method and an apparatus for melting sugar, referred to in the following as solid matter. The apparatus includes at least one melting tube (1) configured as a direct heat exchanger for melting the solid matter with an inlet (2) for the solid, an outlet (3) for the liquid produced by melting the solid matter through a phase transition, an inlet (4) for a heat exchange fluid, and an outlet (5) for the heat exchange fluid. The heat exchange fluid and the solid matter are in direct contact with one another inside the melting tube (1) for the purpose of heat exchange.