A temperature detector of the present invention includes a temperature sensor, a reference signal generation circuit, a level memory which rewritably stores therein a first signal level and a second signal level, a control circuit which controls the reference signal generation circuit so as to make a level of the reference signal change from the first signal level to the second signal level, a comparator circuit which compares the level of the reference signal and a level of the output signal, and a level rewriter which rewrites at least either one of the first signal level and the second signal level. When the level of the reference signal reaches the level of the output signal, the control circuit generates a detected temperature signal, and controls the level rewriter so as to change a range where a level of the reference signal changes.