An infrared solid-state image pickup apparatus includes an SOI substrate having a silicon oxide film layer and an SOI layer on a silicon substrate, a detecting portion which is provided with a PN junction diode formed on the SOI substrate and converts a temperature change generated by an incident infrared ray to an electric signal, and a support that holds the detecting portion with a space from the silicon substrate of the SOI substrate. An impurity in a semiconductor layer constituting the PN junction diode is distributed such that carriers flowing in the semiconductor layer are distributed in such an uneven manner as being much in a central portion of the semiconductor layer than in a peripheral portion thereof.