PURPOSE: To obtain an Ru-Sn catalyst with improved catalytic activity and with which acetic acid, etc., can be produced by using methanol as a single source by one step reaction by a method wherein the cation in a cation exchanger (e.g. zeolite) is cation-exchanged with a complex contg. a positive valent Ru and the cation exchanger is treated with a bi- or tetra-valent tin compd.

CONSTITUTION: The catalyst for synthesis of acetic acid or methyl acetate is obtd. by using a cation exchanger (e.g. zeolite), an Ru complex contg. positive valent Ru carried on the cation exchanger by means of cation exchange (e.g. an Ru ammine complex) and a tin compd. with zero-, bi- or tetra-valence carried on the cation exchanger (e.g. tin (I) halide)). This catalyst exhibits high catalytic activity and acetic acid or methy acetate can be produced with this catalyst by using methanol as a single source by one step reaction. In addition, the high catalytic activity can be kept for a long period and acetic acid or methyl acetate can be prepd. therewith with a high selectivity.