According to one embodiment, an infrared detection device includes a detection element. The detection element includes a semiconductor substrate, a signal interconnect section, a detection cell and a support section. The semiconductor substrate is provided with a cavity on a surface of the semiconductor substrate. The signal interconnect section is provided in a region surrounding the cavity of the semiconductor substrate. The detection cell spaced from the semiconductor substrate above the cavity includes a thermoelectric conversion layer, and an absorption layer. The absorption layer is laminated with the thermoelectric conversion layer, and provided with a plurality of holes each having a shape whose upper portion is widened. The support section holds the detection cell above the cavity and connects the signal interconnect section and the detection cell.