To provide an apparatus which enables a sufficient sleeping to be achieved in such a manner that the variation of a sleeping cycle during sleeping is detected to keep an optimal in-bed temperature in response to the sleeping cycle.

This in-bed temperature controlling apparatus is constituted of a sleeping depth judging means 2, a temperature measuring means 3, a temperature regulating means 4, and a temperature controlling means 5. That is, a sleeping depth is judged from a detailed biomedical signal of a subject by the sleeping depth judging means 2. Also, a temperature in bed is measured by the temperature measuring means 3 consisting of a temperature sensor such as a thermistor. Temperature regulating sheets 7a and 7b are controlled by the temperature controlling means 5 in such a manner that the temperature in bed may be regulated to a proper temperature in response to the sleeping depth at the time of sleeping.