An infrared sensor IC and an infrared sensor, which are extremely small and are not easily affected by electromagnetic noise and thermal fluctuation, and a manufacturing method thereof are provided. A compound semiconductor that has a small device resistance and a large electron mobility is used for a sensor (2), and then, the compound semiconductor sensor (2) and an integrated circuit (3), which processes an electrical signal output by the compound semiconductor sensor (2) and performs an operation, are arranged in a single package using hybrid formation. In this manner, an infrared sensor IC that can be operated at room temperature can be provided by a microminiature and simple package that is not conventionally produced.