<p>In an ammonia sensor ( 1 ), lead portions ( 7 ) and ( 9 ) are provided on an insulating substrate ( 5 ); a pair of comb-shaped electrodes ( 11 ) and ( 13 ) are connected to the lead portions ( 7 ) and ( 9 ), respectively; a sensitive layer ( 15 ) is provided on the comb-shaped electrodes ( 11 ) and ( 13 ); and a protective layer ( 17 ) is provided on the sensitive layer ( 15 ). Particularly, the sensitive layer ( 15 ) is formed of a gas-sensitive raw material predominantly containing ZrO<SUB>2 </SUB>and containing at least W in an amount of 2 to 40 wt. % as reduced to WO<SUB>3</SUB>.</p>
