The wall-jet ring disk electrode (WJRDE) has been used with a thin layer cell in a flow system. Usually, the cavity for the solution flow and reactions on the ring disk electrode (RDE) is formed with an elastomer spacer. Accordingly, the thickness is more than several tenths of a micrometer. If a very thin-layered WJRDE (TLWJRDE) is fabricated, the collection efficiency N, which indicates the rate at which the product on the disk is captured onto the ring electrode, is expected to increase. Therefore, a TLWJRDE was prepared in a very thin cavity and was fabricated by micromachining. Ditches and the cavity were formed on a glass plate by photolithography and chemical etching. and this chip was pasted onto another glass substrate prepared with the RDE on it. The sample solution was introduced from the center of the device, and was spread over the electrodes. After this, it went out from the periphery of the device. The TLWJRDE was evaluated using the Fe(CN)(6)(4-/3-) redox system, and its characteristics are discussed. When the flow rate was decreased, N increased to nearly 100%. This tendency was stronger, especially when the flow-through cell was thinner. Compared to other RDEs reported previously, a very thin cavity of micrometer order can be fabricated, and large N values were obtained in the TLWJRDE system. The TLWJRDE can be manufactured by micromachining and is expected to be used as a disposable detector.