PURPOSE: To enable a highly sensitive detection of organic substance low in the vapor pressure at the normal temperature by providing a heater for heating both of a gas detection element and material to be detected.

CONSTITUTION: A metal oxide semiconductor such as SnO2 is applied on a substrate 2 and a detection element 1 with a pair of electrodes is so arranged on the surface of the substrate to take a resistance value through a pin 3. A heater 4 is inserted through the substrate to heat both of the element 1 and material to be detected. A projection 8 is provided on the undersurface of a cover 7 housing it to keep the material being detected at a fixed distance from the heater. When the heater 4 is energized through the pin 5 with the cover 7 contacting the material being detected, heat of heater 4 transmits to the material through an explosion proof metal screen 6 to vaporize a volatile organic substance in the material which touches the gas detection element 1 to amplify the detection resistance thereof to be fed to a buzzer or a meter. This enables a highly sensitive detection of organic substance even low in the vapor pressure at the normal temperature free from effect of ambient air current or the like.