PROBLEM TO BE SOLVED: To provide a temperature estimation method capable of estimating a temperature at a place to which electricity is not supplied.SOLUTION: Each of thermal difference power generation chips 41 and 51: has two thermosensitive sections； is installed in a manner that exposes one thermosensitive section indoors and the other thermosensitive section to external air； generates electric power using a temperature difference between an indoor temperature and an external temperature； and stores the generated electric power. A radio device which receives an electric power supply from the thermal difference power generation chips 41 and 51 transmits a signal. When acquiring receipt notification of a signal from a receiver which receives the signal transmitted from the radio device, a computer: counts the number of receipt of the signal in a predetermined period； reads out a temperature difference corresponding to the counted number of receipt from a storage section which stores a correspondence relation of the number of receipt in the predetermined period with the temperature difference between the thermosensitive sections of the thermal difference power generation chips 41 and 51； acquires the external temperature； and estimates the indoor temperature at installation positions of the thermal difference power generation chips 41 and 51 on the basis of the read temperature difference and the acquired external temperature.
