An analog-to-digital (AD) converting apparatus includes a register, a selecting section and an AD converting section. The register holds a channel specifying data indicating whether each of a plurality of analog signals should be subjected to an AD conversion. The selecting section is connected with a plurality of analog input channels from which the plurality of analog signals are supplied, and sequentially selects ones of the plurality of analog input channels based on the channel specifying data held by the register. The AD converting section carries out the AD conversion of the analog signals on the selected analog input channels into digital signals in order. The channel specifying data contains a plurality of channel data corresponding to the plurality of analog input channels, and each of the plurality of channel data is set when the AD conversion should be carried out to the analog signal on the analog input channel corresponding to the set channel data.