We applied a microreactor to the synthesis of polymethylmethacrylate (PMMA) using a laboratory microreactor system with a production volume of 2-3 t per year, which enabled pseudo-continuous feeding by syringe pumps. When using a tube made of stainless steel, the values of the yield, number average molecular weight (M-n), and polydispersity index (PDI) reached 75.2%, 9.4 x 10(3), and 1.88, respectively. These results were in good accordance with the reported ones and a product with comparable properties was obtained. Then, we performed a continuous synthesis of PMMA for 8 h using a medium scale microreactor plant with a production volume of 100 t per year, which provided continuous feeding by triple cam driven pumps. When using a tube made of polytetrafluoroethylene (PTFE), it was con firmed that a product was continuously obtained for 8 h, whose yield, M-n, and PDI were on average 66.2%, 8.8 x 10(3), and 1.95, respectively. The variation in the yield, M-n, and PDI was within 5.7%, 4.5%, and 1.0%, respectively. For comparison, when using the laboratory microreactor system under the same reaction condition with a tube made of PTFE, the corresponding values of the yield, M-n, and PDI were 66.5%, 8.4 x 10(3), and 2.04, respectively. The difference in the results between the above two microreactor systems was 4.8% at a maximum (in M-n). Therefore, the synthesis of PMMA was continuously performed using the medium scale microreactor plant and the comparability of the reaction performance between the above two microreactor systems was ensured.