Sensing device and method of detecting target substance

A sensing device comprising:

• a gas sampler that incorporates a gaseous sample or a part of a component of the sample into a liquid by causing the sample to pass through a filter structure to perform gas-liquid conversion, the filter structure having an enzyme detachably immobilized thereon, activity of the enzyme being inhibited by binding of a target substance;
• an enzyme capture tank that captures an enzyme detached from the filter structure and a complex of the target substance and the enzyme detached from the filter structure;
• a substrate tank that supplies a substrate solution to the enzyme capture tank;
• and
• a sensor that performs sensing of an amount of a substrate or an amount of a product contained in the substrate solution supplied to the enzyme capture tank.