A humidity sensing device based on a new humidity sensing principle is designed and fabricated in this study. The silicon thermopile is consisted of 25 couples of p-type diffused layer/Al strips. The internal resistance and the Seebeck coefficient are 300kl and 537$mu$V/K, respectively Fabricated sensors showed linear response characteristics proportional to relative humidity changes with a sensitivity of 9$mu$V/%RH in the range from 20% to 90%.