Disclosed is a temperature sensor using a work-function-difference-based radiant-ray detecting element that outputs, as a detecting signal of radiant rays, a work function difference between gate electrodes of first and second field-effect transistors sensing the radiant rays. The temperature sensor includes at least a pair of a first work-function-difference-based radiant-ray detecting element having a positive output temperature coefficient; and a second work-function-difference-based radiant-ray detecting element having a negative output temperature coefficient of which an absolute value is equal to an absolute value of the output temperature coefficient of the first work-function-difference-based radiant-ray detecting element.