To provide a toilet seat allowing stable measurement of a body temperature even when a temperature sensor is installed to the toilet seat and enabling a subject to care about health by unconsciously using the body temperature, since merely incorporating a general temperature sensor to the toilet seat does not allow precise measurement of the body temperature, although these days it is proposed in many places that toilet environments are used to acquire personal biological information and to facilitate health care and as one important measured objects, the body temperature is daily measured.

The temperature of a toilet seat body is set to an arbitrary temperature by a built-in heater. After the subject contacts a seat surface, a temperature difference between near the seat surface and inside the main body is measured by a temperature difference measuring instrument, and at the same time, the temperature of the seat surface is measured as well. The temperature of the main body is changed by changing output of the heater and the body temperature which reflects an internal temperature of the body is measured by calculating the temperature when the temperature difference becomes zero by measuring twice or more in different seat surface temperatures.