A thermal type infrared sensor and a method of manufacturing the same that have a high degree of freedom of structure and a low cost. An infrared ray detecting portion and a support leg are formed above flat plate-shape void formed inside of a semiconductor substrate, and a processing circuit section of a signal from a detecting portion is fabricated on the semiconductor substrate. Because the structure of the processing circuit section is not influenced by a substrate structure, characteristics are improved. Furthermore, the structure is simplified, and it is possible to reduce a manufacturing cost.