In a process for producing a (meth)acrylic acid compound by catalytic vapor phase oxidation, the (meth)acrylic acid compound is produced constantly and efficiently by preventing the change in the composition of the raw material mixed gas, the abnormal temperature increase in the oxidation reactor and the deterioration of the catalytic activity or the useful catalyst life. In the process for producing (meth)acrolein or (meth)acrylic acid by the catalytic vapor phase oxidation reaction of propylene, propane or isobutylene in the oxidation reactor, the temperature of the raw material mixed gas introduced to the oxidation reactor is maintained to be at least the dew point temperature of the raw material mixed gas.