A reaction processor for performing a reaction process of a sample by applying a thermal cycle to the sample while the sample moves inside a channel of a reaction processing vessel, the reaction processor comprising: a liquid feeding system for controlling the pressure inside the channel of the reaction processing vessel in order to move and stop the sample inside the channel, wherein the liquid feeding system includes: a pressurizing chamber; a first liquid feeding pump that is arranged inside the pressurizing chamber; and a second liquid feeding pump that is arranged inside the pressurizing chamber, wherein the output of the first liquid feeding pump communicates with a first communication port that is provided at one end of the channel of the reaction processing vessel, and wherein the output of the second liquid feeding pump communicates with a second communicationport that is provided at the other end of the channel of the reaction processing vessel, wherein the liquid feeding system further comprises a control unit for controlling the first liquid feeding pump and the second liquid feeding pump in order to move the sample inside the channel, and wherein the liquid feeding system is arranged to maintain the pressure inside the channel to be higher than the air pressure in the surrounding environment of the reaction processor during the reaction process of the sample by maintaining the internal pressure inside the pressurizing chamber to be higher than the air pressure in the surrounding environment of the reaction processor. a liquid feeding system for controlling the pressure inside the channel of the reaction processing vessel in order to move and stop the sample inside the channel, wherein the liquid feeding system includes: a pressurizing chamber; a first liquid feeding pump that is arranged inside the pressurizing chamber; and a second liquid feeding pump that is arranged inside the pressurizing chamber, wherein the output of the first liquid feeding pump communicates with a first communication port that is provided at one end of the channel of the reaction processing vessel, and wherein the output of the second liquid feeding pump communicates with a second communicationport that is provided at the other end of the channel of the reaction processing vessel, wherein the liquid feeding system further comprises a control unit for controlling the first liquid feeding pump and the second liquid feeding pump in order to move the sample inside the channel, and wherein the liquid feeding system is arranged to maintain the pressure inside the channel to be higher than the air pressure in the surrounding environment of the reaction processor during the reaction process of the sample by maintaining the internal pressure inside the pressurizing chamber to be higher than the air pressure in the surrounding environment of the reaction processor. a pressurizing chamber; a first liquid feeding pump that is arranged inside the pressurizing chamber; and a second liquid feeding pump that is arranged inside the pressurizing chamber, wherein the output of the first liquid feeding pump communicates with a first communication port that is provided at one end of the channel of the reaction processing vessel, and wherein the output of the second liquid feeding pump communicates with a second communicationport that is provided at the other end of the channel of the reaction processing vessel, wherein the liquid feeding system further comprises a control unit for controlling the first liquid feeding pump and the second liquid feeding pump in order to move the sample inside the channel, and wherein the liquid feeding system is arranged to maintain the pressure inside the channel to be higher than the air pressure in the surrounding environment of the reaction processor during the reaction process of the sample by maintaining the internal pressure inside the pressurizing chamber to be higher than the air pressure in the surrounding environment of the reaction processor.