A breath detection device includes a breath-blowing unit in which breath is blown; a deflection amount sensor that detects pressure of the breath-blowing unit; a temperature sensor that detects a physical amount (temperature) different from the pressure of the breath-blowing unit; a storage unit that stores a determination reference which is a reference to determine whether or not breath is blown into the breath-blowing unit; and a determination unit that compares a detection result which is detected by the deflection amount sensor and the temperature sensor with the determination reference, and determines whether or not breath is blown into the breath-blowing unit.