The present invention relates to a method of surface-treating an aluminum heat exchanger for vehicles in which a sufficient amount of photocatalytic metal oxide particles are retained on a surface of the heat exchanger in a state capable of exhibiting a photocatalytic activity thereof to remove VOC in a compartment of the vehicles by irradiating an ultraviolet ray thereto in an efficient manner. The method of surface-treating an aluminum heat exchanger for vehicles according to the present invention includes (1) a step of dispersing photocatalytic metal oxide particles whose surface is modified with apatite in an aqueous solution in which a low-temperature heat-decomposable resin is dissolved, to prepare a slurry; (2) a step of applying the slurry onto a surface of the heat exchanger; and (3) a step of drying the heat exchanger at a temperature of from 150 to 280° C. to decompose and remove a part of the low-temperature heat-decomposable resin on the surface of the photocatalytic metal oxide particles.