Disclosed is an infrared sensor wherein variance of an S/N ratio within the surface of an infrared sensor chip due to heat generated by an IC chip can be suppressed. The infrared sensor is provided with: the infrared sensor chip (100), wherein a plurality of pixel sections (2) are disposed in the form of an array on one surface of a semiconductor substrate (1), each of said pixel sections being provided with a temperature-sensitive section (30) configured of a thermopile (30a); and the IC chip (102) which processes output signals outputted from the infrared sensor chip (100). A package (103) has: a package main body (104) wherein the infrared sensor chip (100) and the IC chip (102) are mounted by being horizontally disposed; and a package cover (105), which has a lens (153), which transmits infrared rays, and which is hermetically bonded to the package main body (104). The package (103) has, inside thereof, a cover member (106), which has a window hole (108) that passes infrared rays to the infrared sensor chip (100), and which makes uniform the temperature change quantities of the hot junctions (T1) and the cold junctions (T2) of the pixel sections (2), said temperature change quantities corresponding to heat generated by the IC chip (102).