To achieve rapid intraparticle diffusion when metal-organic frameworks are used as adsorbents and/or catalysts, it is preferable to reduce their crystal size and improve their monodispersity. The simplest method for reducing the crystal size in a synthetic aqueous solution is increasing the ligand concentration. However, this produces an environmental load, because a large amount of ligand remains in the waste solution. In this study, size-controlled synthesis of the zeolitic imidazolate framework 67 (ZIF-67) was achieved by using a fine liquid droplet as the reaction field. This droplet was generated by electrospraying in the liquid phase, which improved the crystal size, morphology, and monodispersity of ZIF-67.