In this study, the effect of flow disturbance such as contraction, expansion pipe and velocity deviation from low velocity of $0.1;^m/s$ to $2.5;^m/s$ on the error characteristics of the flowmeter was studied. Flow experiments using flowmeter calibration facility of K-water were undertaken for the cases of ultrasonic flowmeter based on transit-time method and electromagnetic flowmeter. Experimental results are presented that measurement error of expansion pipe are larger than contraction pipe. It is shown that the minimum straight length were required to remain of ${pm}0.5%$ error for electromagnetic flowmeter and ${pm}2.0%$ error for ultrasonic flowmeter.