A process for preparing trans-.beta.-benzoylacrylic acid ester having the general formula (I): ##STR1## wherein R is alkyl group or aralkyl group, which comprises dealcoholizing .beta.-benzoyl-.alpha.-alkoxypropionic acid ester having the general formula (II): ##STR2## wherein R is above, in the presence of an acid catalyst to give trans-.beta.-benzoylacrylic acid ester having the general formula (I).According to the process of the present invention, the by-product (II) produced in the esterification reaction of .beta.-benzoylacrylic acid (III) with the alcohol (V) by the dehydration reaction can be converted into the compound (I) by the dealcoholization reaction in the presence of the acid catalyst and thus trans-.beta.-benzoylacrylic acid ester (I) with a high purity can be produced in an industrially advantageous manner.