The present invention provides a process for catalytic vapor phase oxidation which prevents runaway reaction or early deterioration of a catalyst, in the production of (meth)acrylic acid or the like from propylene or isobutylene by the catalytic vapor phase oxidation process using a multi-tubular reactor, which can lead to the production thereof constantly in high yield for a long period of time. Further, the present invention provides a process for catalytic vapor phase oxidation wherein raw material gas is introduced for oxidation into reaction tubes of a multi-tubular reactor which is equipped with, as arranged within the shell of the reactor, a plurality of reaction tubes having a catalyst packed therein and a plurality of baffle plates for changing the direction of the flow of a heating medium introduced into the shell, characterized in that the temperature of the catalyst packed in a reaction tube which is not connected with at least one baffle plate is measured at plural points in the direction of an axis of the reaction tube.