A dynamic differential scanning calorimeter (dynamic DSC) works simultaneously as a differential scanning calorimeter and an AC calorimeter, using the same apparatus with AC temperature modulation superposed on a linear temperature ramp. From the AC calorimetric (ACC) operation, we can determine the absolute value of the heat capacity by making the best of the twin-type apparatus, although the temperature resolution is a little lower than in a high precision AC calorimeter. In addition, it should be pointed out that in the ACC operation, heat capacity can be determined easily in comparison with differential scanning calorimetric (DSC) operation. Therefore, at a second order phase transition, the ACC operation is useful for obtaining linear heat capacity and furthermore, the frequency dispersion of linear heat capacity is obtainable. On the other hand, at a first order phase transition, the situation is complicated. In this case, we have to pay attention to non-linear heat capacity. The analysis of the waveform of AC temperature observed at a steady temperature might be useful to obtain evidence for the kinetic mechanism.