A gas detection system includes a first sensor unit that outputs a voltage corresponding to a concentration of a specific gas, a storage tank capable of storing a sample gas or a purge gas to be supplied to the first sensor unit, and a control unit. The control unit detects a type and a concentration of a gas contained in the sample gas on the basis of a detection result of the first sensor unit. The control unit sets a collection period during which a gas in a predetermined space is collected into the storage tank as the sample gas or the purge gas and a supply period during which the sample gas or the purge gas is supplied to the first sensor unit such that the collection period and the supply period fall in different time slots.