A sensing device that adsorbs a substance to be sensed as a gas to a piezoelectric resonator , changes a temperature of the piezoelectric resonator to desorb the substance to be sensed, and senses the substance to be sensed based on a relationship between a change of an oscillation frequency of the piezoelectric resonator and the temperature, the sensing device comprising: a substrate that holds the piezoelectric resonator and a temperature detector to detect a temperature of the crystal resonator ; a thermoelectric element unit , disposed at a position in contact with the substrate to change the temperature of the piezoelectric resonator ; a support plate that supports the thermoelectric element unit from an opposite side of the position in contact with the substrate ; a base portion to which the support plate is secured such that a surface on an opposite side of the surface to support the thermoelectric element unit is in contact with the base portion , the base portion performing at least one of heat supply and heat dissipation to the thermoelectric element unit via the support plate ; a housing space included in the base portion that houses a circuit board including integrated circuits which include an oscillator circuit to oscillate the piezoelectric resonator ; sockets as electrodes connected to the integrated circuits respectively; and pins as rod-shaped conductive members, removably disposed between electrodes connected to the piezoelectric resonator or the temperature detector and each of the sockets respectively, wherein the substrate , the thermoelectric element unit , and the support plate are integrated to form a sensing module unit removable from the base portion ; and, wherein the pins are able to switch, by being inserted into and pulled out from the sockets , electrical connection and disconnection between the piezoelectric resonator and the temperature detector on the substrate , and the integrated circuits in the base portion . a substrate that holds the piezoelectric resonator and a temperature detector to detect a temperature of the crystal resonator ; a thermoelectric element unit , disposed at a position in contact with the substrate to change the temperature of the piezoelectric resonator ; a support plate that supports the thermoelectric element unit from an opposite side of the position in contact with the substrate ; a base portion to which the support plate is secured such that a surface on an opposite side of the surface to support the thermoelectric element unit is in contact with the base portion , the base portion performing at least one of heat supply and heat dissipation to the thermoelectric element unit via the support plate ; a housing space included in the base portion that houses a circuit board including integrated circuits which include an oscillator circuit to oscillate the piezoelectric resonator ; sockets as electrodes connected to the integrated circuits respectively; and pins as rod-shaped conductive members, removably disposed between electrodes connected to the piezoelectric resonator or the temperature detector and each of the sockets respectively, wherein the substrate , the thermoelectric element unit , and the support plate are integrated to form a sensing module unit removable from the base portion ; and, wherein the pins are able to switch, by being inserted into and pulled out from the sockets , electrical connection and disconnection between the piezoelectric resonator and the temperature detector on the substrate , and the integrated circuits in the base portion . <EOS>