This study is an attempt to prepare proton conductors based on ammonium polyphosphate (NH4PO3). The base material itself is almost an insulator, but becomes appreciably proton-conductive by thermally decomposing NH4PO3 to HPO3. The NH4PO3-HPO3 mixture obtained has the maximum conductivity of 5 x 10(-3) S/cm at 300 degrees C, but is apt to melt at this temperature. To increase the melting point, (NH4)(2)SiP4O13 and Al(PO3)(3) were added as framework materials. The composite materials obtained were able to keep solid states at 400 degrees C and attained a conductivity of 0.1 S/cm at this temperature. Above this temperature, the conductivity decreased with increasing temperature owing to dehydration which results in a loss of proton.