To detect a desired range of detection area through a single sensor at a substantially equal sensitivity by providing a temperature sensor having a container (tube) encapsulating fluid in a detection area and detecting the temperature based on the inner pressure of the container.

A tube 2 encapsulating a fluid, e.g. air, is closed at one end 2a thereof and coupled, at the other end 2b thereof, with the pressure introduction opening 3a of a micro pressure sensor 3 thus constituting a temperature sensor 1. The micro pressure sensor 3 detects variation in the pressure of fluid, e.g. air, encapsulated in the tube 2 being applied to the pressure-sensitive plane through the pressure introduction opening 3a as the variation of capacitance and delivers a frequency, pulse or voltage signal. The tube 2 of the temperature sensor 1 is laid to creep on the dial or key hole of a cashbox door and inner pressure variation of the tube 2 incident to expansion or contraction of air caused by temperature variation in the detection area is detected by means of the micro pressure sensor 3. It is then converted into a temperature through an operating circuit and displayed or an alarm is delivered when the output from the micro pressure sensor 3 exceeds a specified threshold level.