A PCR device comprising: a reaction container including a substrate, a channel forming plate and a cover plate, wherein the substrate and the cover plate are fixed with the channel forming plate interposed therebetween, wherein the substrate, the channel forming plate and the cover plate form an annular tubular ring channel of circular annular shape, wherein the annular tubular ring channel is a circular annular chamber having a flow path for a reaction solution with a rectangular cross-section between an outer diameter and an inner diameter of the annular tubular ring channel, and wherein the annular tubular ring channel is disposed such that a diametrical direction of the annular tubular ring channel stands up in a vertical direction to carry out polymerase chain reaction; an electrode pair consisting of two electrodes disposed on one inner surface between the opposed substrate and channel forming plate to form the reaction container, disposed to face each other with a gap interposed therebetween, said gap extending across an entire width of the flow pathand intersecting the flow path on one side of the annular tubular ring channel, and the gap having a horizontally aligned gap center line; and a control unit which is configured to apply an AC voltage to the electrode pair to make an AC current flow through the reaction solution, thereby generating Joule heat to make the reaction solution flow vertically upwards at the position of the gap of the electrode pair on the side of the annular tubular ring channel to intersect the gap center line and to control the reaction solution in temperature. a reaction container including a substrate, a channel forming plate and a cover plate, wherein the substrate and the cover plate are fixed with the channel forming plate interposed therebetween, wherein the substrate, the channel forming plate and the cover plate form an annular tubular ring channel of circular annular shape, wherein the annular tubular ring channel is a circular annular chamber having a flow path for a reaction solution with a rectangular cross-section between an outer diameter and an inner diameter of the annular tubular ring channel, and wherein the annular tubular ring channel is disposed such that a diametrical direction of the annular tubular ring channel stands up in a vertical direction to carry out polymerase chain reaction; an electrode pair consisting of two electrodes disposed on one inner surface between the opposed substrate and channel forming plate to form the reaction container, disposed to face each other with a gap interposed therebetween, said gap extending across an entire width of the flow pathand intersecting the flow path on one side of the annular tubular ring channel, and the gap having a horizontally aligned gap center line; and a control unit which is configured to apply an AC voltage to the electrode pair to make an AC current flow through the reaction solution, thereby generating Joule heat to make the reaction solution flow vertically upwards at the position of the gap of the electrode pair on the side of the annular tubular ring channel to intersect the gap center line and to control the reaction solution in temperature.