An electrochemical humidity sensor was fabricated with poly(1,5-diaminonaphthalene) film coated on a gap of two splitted gold electrodes, which were made by vacuum deposition. Response currents according to humidity were measured by the potential sweep method and chronoamperometry. The stability of the polymer film was improved by double step chronoamperometry using the applied voltage of ${pm}0.5$ Vdc. The response time determined by the pulse technique was about ${sim}50$ msec and the relative standard deviation of current response was within ${pm}5.0%$. The response current of the film was intrinsically humidity dependent. The film exhibited a non-linear but reproducible response in ordinary range of relative humidity. The linear equations were $I(nA)=0.28{ imes}%RH-1.01$ between 10 to 70 %RH and $I(nA)=6.05{ imes}%RH-403.21$ between 70 to 90 %RH.