A pressure sensor for detecting a pressure and for outputting a signal based on the piezoresistance effect includes a substrate having a sensor chip on one side in a thin portion and a concave portion on another side, a piezo-resistor in the sensor chip, a pedestal being attached to the substrate and having a through hole for introducing the pressure to the sensor chip and a gel material filled in the concave portion and the through hole for protecting the sensor chip. A ratio of a diameter of the through hole to a thickness of the pedestal is substantially within a range between 1 and 3.