Acetic acid is manufactured by carbonylating methanol with carbon monoxide by way of a heterogeneous catalytic reaction in a bubble column reactor. The carbonylating reaction is conducted with a solid catalyst concentration of not less than 100 kg/m3 in terms of the reaction volume. For the reaction, the partial pressure of carbon monoxide in the reactor is confined to a range between 1.0 and 2.5 MPa while the exhaustion ratio of carbon monoxide is confined to a range between 3 and 15% of the theoretical reaction volume of carbon monoxide and the liquid superficial velocity is made to be found in a range between 0.2 and 1.0 m/sec.