Provided is a method for preparing glycolic acid which comprises oxidizing glycolaldehyde with molecular oxygen in the presence of a solvent and a supported catalyst. Said supported catalyst comprises (i) a noble metal selected from the group consisting of Pt, Pd, Ru and Rh, (ii) Bi and (iii) a support. Advantageously, the supported metallic catalyst is more active than the catalysts used in prior art. Furthermore, the catalyst is more stable at oxygen rich conditions.