To provide a modulation device having high code quality by deciding a DSV (Digital Sum Value) control bit by the number of times of appearance of the minimum reversal interval in each reversal interval independently of integrated DSV.

This device has a DSV control bit inserting part 11 inserting different DSV control bits and generating a first data column and a second data column, a modulating part 12 converting the first data column and the second data column to a code word column using a conversion rule in which the minimum reversal interval Tmin is prescribed and modulating it, a reversal interval calculating part 27 calculating a time from reversion of the previous time in each code word column as a reversal interval, and a minimum reversal interval appearance number calculating part 28 calculating the number of times of appearance of the minimum reversal interval in each reversal interval. The device is provided with a code word column selecting part 13 selecting a less code word between the first minimum reversal interval appearance number and the second minimum reversal interval appearance number when the first integrated DSV value and the second integrated DSV value are the same.