There is provided a monitoring apparatus including a gas sampling apparatus and a sensor that detects a chemical substance included in gas obtained by the gas sampling apparatus. The gas sampling apparatus includes: an air supplying unit that forms an air curtain to form a space that covers a region to which an object to be monitored is included and which is separated from the outside environment; a sampling unit that extracts the gas inside the separated space; and a diffusion gas supplying unit that supplies, into the separated space, an amount of diffusion gas that is at least equal to the sampled amount of the sampling unit, wherein the sampling unit includes a plurality of sampling nozzles disposed at three-dimensionally different positions inside the separated space.