PURPOSE: To prepare an aldehyde at a low cost, by oxidizing an alcohol at a low reaction temperature using an oxidation catalyst comprising fine powder of titanium hydride which is an easily available stable compound.

CONSTITUTION: An aldehyde such as acetaldehyde is prepared by oxidizing an alcohol such as ethanol at a relatively low temperature, i.e. about 50°C, using fine powder of titanium hydride having a particle diameter of about 0.1W50μ as the catalyst. The reaction can be carried out without using particular reactor or reaction apparatus, and the storage of the catalyst is easy.