A heat sensor (1) includes: a housing (10) of a cylindrical shape which has a bottom part (11) and a side part (12); and a heat detection unit (30) provided in the housing (10) and configured to be detect heat, wherein the housing (10) has a first hole (21) and a second hole (22) from one side of which gas flows in and from another side of which the gas flows out, the first hole (21) is provided in at least one of the bottom part (11) and the side part (12), the second hole (22) is provided in at least one of the bottom part (11) and the side part (12), and when the heat sensor (1) is viewed from a central axis (J1) of the housing (10), each of the first hole (21) and the second hole (22) is provided in a peripheral region (10b) different from a center (10a) of the housing (10), and the heat detection unit (30) is provided in the peripheral region (10b) when the heat senor (1) is viewed from a central axis (J1) of the housing (10).