Cu oxide nano powders were synthesized by the levitational gas condensation (LGC) method, and heated at temperature ranges from 150 to 450 C. The nano powders consist of mainly Cu2O with an average size of 35 nm. The analysis of the IR-spectra of the nanopowders demonstrates that the surface of the sample under an air exposure is coated by hydroxylhydride (-OH, H2O) and hydroxycarbonated [Cu2(OH)2CO3]. The change of the particle size by heat treatment below 450 °C is relatively small. The variation of the adsorption ability is mainly defined under heating at least up to 300 °C, by the surface state of the particles. The catalytic effect was increased at heat treated samples.