A reaction container 10 of the PCR device 1 has a tubular ring channel 20 formed by a substrate 11, a channel forming plate 12, and a cover plate 13. The ring channel 20 comprises an electrode pair 21 disposed, in a diametrical direction of an inner surface of one side wall of the ring channel 20, to face each other with a horizontal gap interposed therebetween, and is vertically erected. The gap length of the electrode pair 21 is across the entire width within a cross-section of the ring channel 20.