Two kinds of humidity sensor are made, one by anodizing pure aluminum and the other by evaporation Sn02 on the anodized pure alumia film, and their electrical characteristics are investigated in various humidity atmosphere. The change of surface resistance with humidity of $AI_2O_3/AI$ and $SnO_2-AI_2O_3/Al$ sensors are found to be $1.40 imes 10^{-2}Omega$/RH and $1.56 imes 10^{-2}Omega$/RH, respectively. The hysteresis phenomena associated with the irreversibility of surface resistance-humidity is less in $SnO_2-AI_2O_3/Al$ sensor than in $AI_2O_3/AI$. It is concluded that $SnO_2-AI_2O_3/Al$ film can be used as humidity sensor in room temperature region because temperature dependence of surface resistance of the film is found to be as $0.56 imes 10^{-2} Omega /^{circ}C$ in O~ $20^{circ}C$ range, where as $2.50 imes 10^{-2} Omega /^{circ}C$ in 40-$50^{circ}C$.