A successive approximation A/D converter, includes a reference voltage generation circuit, a sample/hold circuit, a D/A converter circuit, a comparator, and a control circuit. A potential difference between the comparison target voltage generated by the D/A converter circuit and the internal analog voltage is applied to one input terminal of the comparator through a first signal line, and the reference voltage generation circuit is connected to the other input terminal of the comparator through a second signal line and a switch. Capacitive elements are disposed between the high potential power supply and the second signal line, and between the second signal line and the low potential power supply, respectively. The control circuit turns ON the switch to charge the first and second capacitive elements during a period when the sample/hold circuit samples and holds the internal analog voltage and turns OFF the switch in response to end of the period.