A deep body thermometer includes an upper exterior body that is made of a foamed material of closed cells or semi-closed cells having waterproof properties and is formed in a substantially hat-like shape in side view, a lower exterior body that has a peripheral edge in close contact with the upper exterior body, a sticking member that has adhesiveness and one surface of which is stuck to an outer side surface of the lower exterior body, and a wiring substrate that is accommodated in a space defined by the upper exterior body and the lower exterior body. The upper exterior body includes stress relieving portions that extend in the direction intersecting with the direction in which stress generated by external force acts and are smoothly curved with respect to the direction in which the stress acts so as to relieve the stress.
