A heating cooker, comprising: a body; an inner case disposed at an inside of the body, and provided at an inside thereof with a cooking compartment at which food is being cooked; a detection hole formed at a wall of one side of the inner case, and configured to allow an infrared ray generated in the cooking compartment to be released to the outside of the cooking compartment; and an infrared ray detecting apparatus comprising: a reflecting mirror configured to change a path of an incident infrared ray, and an infrared ray sensor configured to receive the infrared ray having the path thereof changed to detect an intensity of the received infrared ray, characterized in that said reflecting mirror comprises a plurality of reflection surfaces ( 232, 234, 236), wherein each of the plurality of reflection surfaces (232, 234, 236) comprises a reflection surface having a constant curvature or a reflection surface having a flat surface, and wherein the reflection surfaces (232, 234, 236) are disposed at different inclinations, such that each of the reflecting surface (222, 234) receives the infrared rays being delivered from a different infrared detection domain, and delines the infrared rays to the light receiving unit. a body; an inner case disposed at an inside of the body, and provided at an inside thereof with a cooking compartment at which food is being cooked; a detection hole formed at a wall of one side of the inner case, and configured to allow an infrared ray generated in the cooking compartment to be released to the outside of the cooking compartment; and an infrared ray detecting apparatus comprising: a reflecting mirror configured to change a path of an incident infrared ray, and an infrared ray sensor configured to receive the infrared ray having the path thereof changed to detect an intensity of the received infrared ray, characterized in that said reflecting mirror comprises a plurality of reflection surfaces ( 232, 234, 236), wherein each of the plurality of reflection surfaces (232, 234, 236) comprises a reflection surface having a constant curvature or a reflection surface having a flat surface, and wherein the reflection surfaces (232, 234, 236) are disposed at different inclinations, such that each of the reflecting surface (222, 234) receives the infrared rays being delivered from a different infrared detection domain, and delines the infrared rays to the light receiving unit. a reflecting mirror configured to change a path of an incident infrared ray, and an infrared ray sensor configured to receive the infrared ray having the path thereof changed to detect an intensity of the received infrared ray, said reflecting mirror comprises a plurality of reflection surfaces ( 232, 234, 236), wherein each of the plurality of reflection surfaces (232, 234, 236) comprises a reflection surface having a constant curvature or a reflection surface having a flat surface, and wherein the reflection surfaces (232, 234, 236) are disposed at different inclinations, such that each of the reflecting surface (222, 234) receives the infrared rays being delivered from a different infrared detection domain, and delines the infrared rays to the light receiving unit.