PURPOSE: To enable detection of the presence of a fine wind velocity, by setting a piezo-electric film in which electrodes are formed on both sides of a high polymer film showing a piezo-electric property in a draft path.

CONSTITUTION: A piezo-electric film type wind velocity detector 1 is so arranged that a piezo-electric film 3 is set in a draft path 2 to detect an inter-electrode voltage thereof 3 with a detection circuit 4. The piezo-electric film 3 can change a voltage between electrodes even for a very weak pressure change and when set in the draft path 2, it permits detection to determine whether a specified fine wind velocity exists or not in the draft path 2. A fixed expanse of the piezo-electric film 3 allows a proper surface detection.