A gas detecting apparatus incorporates a number of gas detecting elements which react with a variety of gases and exhibit gas sensitivities differing from one another in dependence on the gas species. The detection patterns obtained by quantitizing the detection outputs of the gas detecting elements are compared with a plurality of standard patterns prepared previously for assumed combinations of gas species and concentrations thereof. On the basis of the standard pattern which is same or most similar to the detection pattern, the gas species is identified.