A novel electrochemical flow cell system that can be programmed to set arbitrary conditions for flow velocity and concentration has been developed. The system includes an electrochemical flow cell and solution supply devices. The flow cell is a coaxial cylindrical pipe and a working electrode is arranged on the inner shaft. The working electrode protrudes from the inner shaft for stable measurement. The solution supply device can continuously change the flow rate and concentration of the solution to be supplied to the flow cell. Using the measurement system, current can be measured under continuous changes of the flow velocity and of the concentration in a wide range. Therefore, it is possible to evaluate the concentration dependence and flow velocity dependence of an electrode reaction efficiently with great detail. To verify the developed system, the diffusion-limited current is measured under continuous change of the copper ion concentration in the copper sulfate aqueous solution. The measured current was compared with the numerical solution of the diffusion-limited current for annular flow. Results of the comparison demonstrate that the developed system works as designed.