A gas detector includes a detecting element, a circuit board, a housing case having a gas introduction hole, and a metal member which covers the gas introduction hole. The detecting element is disposed under the metal member. The gas detector further includes a detecting element wiring fusing prevention member which is electrically conductive and is electrically connected to a grounding line of the circuit board. The detecting element wiring fusing prevention member is disposed at a position such that the shortest distance between the metal member and the detecting element wiring fusing prevention member is smaller than that between the metal member and the detecting element.