Abstract: In a converting device having two sets of converters, each of which includes planar type semiconductor controlled rectifier elements connected in a bridge configuration, with the converters being connected to a load, in a reverse-parallel configuration, so that the anode of one element is connected to the cathode of its parallel connected element, cooling fins are interposed between the planar type semiconductor controlled rectifier elements so that an individual cooling fin serves to cool directly adjacent elements disposed along the same axis in series with each other. As a result, the number of cooling fins can be sharply reduced. The converting device is especially effective for normal and reverse switching operations of a d.c. motor.