The present invention provides a process for producing 5-iodo-2-methylbenzoic acid through iodination of 2-methylbenzoic acid, the process including, as essential steps, a reaction step of iodinating 2-methylbenzoic acid in the presence of a microporous compound, iodine, an oxidizing agent, and acetic anhydride, and a purification step including sublimation, distillation, crystallization, or a combination of two or more of these. According to the present invention, 5-iodo-2-methylbenzoic acid, which is useful for producing functional chemicals such as drugs, can be produced at high purity and high yield in a simple manner. Since the production process includes a simple reaction step and a simple separation/purification step, the load of purification is mitigated. In addition, the microporous compound such as a zeolite catalyst which has been separated and recovered from the reaction mixture can be repeatedly employed after performing of a simple treatment. Thus, the production process ensures a long service life of catalysts and high efficiency.