An A/D converter has an analog multiplexer stage which selects one of a plurality of first analog signals as a second analog signal, an amplifier stage which amplifies the second analog signal to generate a third analog signal, an A/D conversion stage which converts the third analog signal into a digital signal, and a sequencer which controls those stages. The sequencer performs input switching processing in the analog multiplexer stage on completion of sample hold processing by the A/D conversion stage, when performing a plurality of times of A/D conversion processing sequentially, without waiting for completion of the A/D conversion processing.