A safety thermometer in which power is automatically turned on when a sensor rod for measuring a temperature is taken out. The sensor rod is easily taken in the housing when a force is applied to the sensor rod. A sensor rod slider opposes a tip of the sensor rod and has a sensor contact point for connecting a sensor signal of the sensor rod to a circuit. The housing has a space for receiving the sensor rod, a partition wall and a second space to receive circuit devices. A temperature measurement unit is turned on by receiving a power from a power source unit when it contacts the sensor contact point of the sensor rod slider, the temperature measurement unit being connected to the temperature sensor of the sensor rod through the sensor rod slider to process and output a value detected by the temperature sensor.