Dimethylcarbonate (DMC) has been attracting wide attention as an environmentally benign chemical raw material. To develop a vapor-phase synthesis process of DMC by oxidative carbonylation of methanol, effects of reaction conditions have been investigated over CUCl2/NaOH/activated carbon catalysts. A fluidized-bed reactor is preferable for the vapor-phase DMC synthesis, considering the need for temperature control and continuous catalyst regeneration. Experiments using small-scale (13.3 mmID) and bench-scale (53.5 mmID) fluidized bed reactors were carried out. Bench-scale reaction including catalyst regeneration showed good performance over 200 hours.