Provided is a gas detection apparatus which suppresses occurrences of distortions of the optical path to reduce fluctuations of the gas detection sensitivity. A gas detection apparatus 1 includes a substrate 2; a light emitting element 3 disposed in a first region 21 in a main surface 20 of the substrate 2 for emitting light; a light receiving element 4 disposed in a second region 22 in the main surface 20 of the substrate 2 for receiving the light; a light guide member 5 for guiding the light emitted by the light emitting element 3 to the light receiving element 4; and a joint member 6 joining the substrate 2 and the light guide member 5. The joint member 6 serves as a rotation axis when the light guide member 5 is displaced relative to the substrate 2.