A digital filter is used in an A/D converter and includes a first filter and second filter. The first filter outputs first digital data by performing filter processing on output of an A/D conversion unit included in the A/D converter. The second filter outputs second digital data by performing filter processing on the output of the A/D conversion unit. The second digital data has either a lower resolution or a smaller effective number of bits than the first digital data does. The second filter outputs the second digital data before the first filter outputs the first digital data.