PURPOSE: To prepare an aldehyde and/or ketone, in high yield, by the dehydrogenation of an alcohol using a synthetic mica as a novel dehydrogenation catalyst.

CONSTITUTION: The aldehyde (e.g. formaldehyde) and/or ketone (e.g. acetone) can be prepared by the dehydrogenation of an alcohol, especially a primary or secondary alcohol of formula (R1 and R2 are H or organic group) (e.g. methanol, ethanol, isopropyl alcohol, etc.) using a dehydrogenation catalyst comprising a synthetic mica of formula I (X is cation having a coordination number of 12, e.g. Na, K, Ca, Ba, Rb, Sr, etc.; Y is cation having a coordination number of 6, e.g. Mg, Fe, Ni, Mn, Al, etc.) wherein at least a part of the OH groups are substituted with F (preferably tetrasilicone mica, teniolite, especially, a synthetic mica substituted with univalent or bivalent copper).