Behavior of water flow through micro-apertures has scarcely examined in the region of very stow velocity. We measured velocities against pressures for the water flow through 25micron-meter orifice in a range of low velocity and low Reynolds number(Re=0〜20). It was found that a small difference in water temperature results in a great change in flow characteristics. That is, water flows with about two times larger velocities than the velocity theoretically predicted at 22 degree of Celsius temperature, but water lessens its velocity with time passed and goes to a very small velocity, and at last almost clogs itself 70hours after inception of experiment