An A/D converter comprising: a reference voltage generating circuit generating a reference voltage (Vref), said reference voltage being supplied to a measurement voltage generating circuit and to an A/D converting circuit; the measurement voltage generating circuit generating a measurement voltage (Vm) for temperature measurement that corresponds to an ambient temperature of the A/D converter from the reference voltage; a selecting circuit selecting the measurement voltage (Vm) as an analog input voltage (Vin) to the A/D converting circuit; the A/D converting circuit comparing the analog input voltage (Vin) with the reference voltage (Vref) to convert the analog input voltage (Vin) to a digital output value (Dout); a measured value storing circuit storing therein measured values of the reference voltage in advance by letting the measured values correspond to temperatures; a temperature information holding circuit holding the digital output value (Dout) obtained by the A/D converting circuit converting the measurement voltage as temperature information representing a current ambient temperature of the A/D converter; wherein the selecting circuit selects an external input voltage (VEin) as the analog input voltage (Vin) for output to said A/D converting circuit after selecting the measurement voltage (Vm) as the analog input voltage (Vin); and an output control circuit selecting a measured value corresponding to the temperature information held by said temperature information holding circuit from the measured values stored in said measured value storing circuit and outputting the selected measured value when the digital output value (Dout) obtained by the A/D converting circuit converting the external input voltage is output. a reference voltage generating circuit generating a reference voltage (Vref), said reference voltage being supplied to a measurement voltage generating circuit and to an A/D converting circuit; the measurement voltage generating circuit generating a measurement voltage (Vm) for temperature measurement that corresponds to an ambient temperature of the A/D converter from the reference voltage; a selecting circuit selecting the measurement voltage (Vm) as an analog input voltage (Vin) to the A/D converting circuit; the A/D converting circuit comparing the analog input voltage (Vin) with the reference voltage (Vref) to convert the analog input voltage (Vin) to a digital output value (Dout); a measured value storing circuit storing therein measured values of the reference voltage in advance by letting the measured values correspond to temperatures; a temperature information holding circuit holding the digital output value (Dout) obtained by the A/D converting circuit converting the measurement voltage as temperature information representing a current ambient temperature of the A/D converter; wherein the selecting circuit selects an external input voltage (VEin) as the analog input voltage (Vin) for output to said A/D converting circuit after selecting the measurement voltage (Vm) as the analog input voltage (Vin); and an output control circuit selecting a measured value corresponding to the temperature information held by said temperature information holding circuit from the measured values stored in said measured value storing circuit and outputting the selected measured value when the digital output value (Dout) obtained by the A/D converting circuit converting the external input voltage is output.