A nucleic acid amplification device (1, 2, 2A, 2B, 2C, 2D, 3, 3A, 3B, 3C, 3D, 3E, 3F) comprising: an introduction unit into which a reaction solution including a target nucleic acid is introduced; a nucleic acid amplification reaction section in which at least two temperature zones (141, 142) set to different temperatures by a heater unit are present, for amplifying the target nucleic acid included in the reaction solution introduced into the introduction unit; a channel arranged to pass back and forth or in cyclic fashion through the at least two temperature zones (141, 142), and having a capillary force transport mechanism for feeding the reaction solution by capillary force; a fed solution retention section (160, 160A, 160B, 160C, 160D, 160E, 160F) for retaining the reaction solution; and a discharge unit configured to discharge the reaction solution including the target nucleic acid after amplification, wherein the channel includes a first channel disposed in the nucleic acid amplification reaction section and a second channel disposed in the fed solution retention section (160, 160A, 160B, 160C, 160D, 160E, 160F), a first end of the second channel is connected to the first channel, a second end of the second channel is connected to the discharge unit, and the second channel retains the reaction solution fed from the first channel, wherein a volumetric capacity of the second channel is 10% or more of a total volumetric capacity of the channel, wherein the nucleic acid amplification reaction section is disposed so as to oppose to the heater unit, and the fed solution retention section (160, 160A, 160B, 160C, 160D, 160E, 160F) is disposed so as to not oppose to the heater unit. an introduction unit into which a reaction solution including a target nucleic acid is introduced; a nucleic acid amplification reaction section in which at least two temperature zones (141, 142) set to different temperatures by a heater unit are present, for amplifying the target nucleic acid included in the reaction solution introduced into the introduction unit; a channel arranged to pass back and forth or in cyclic fashion through the at least two temperature zones (141, 142), and having a capillary force transport mechanism for feeding the reaction solution by capillary force; a fed solution retention section (160, 160A, 160B, 160C, 160D, 160E, 160F) for retaining the reaction solution; and a discharge unit configured to discharge the reaction solution including the target nucleic acid after amplification, wherein the channel includes a first channel disposed in the nucleic acid amplification reaction section and a second channel disposed in the fed solution retention section (160, 160A, 160B, 160C, 160D, 160E, 160F), a first end of the second channel is connected to the first channel, a second end of the second channel is connected to the discharge unit, and the second channel retains the reaction solution fed from the first channel, wherein a volumetric capacity of the second channel is 10% or more of a total volumetric capacity of the channel, wherein the nucleic acid amplification reaction section is disposed so as to oppose to the heater unit, and the fed solution retention section (160, 160A, 160B, 160C, 160D, 160E, 160F) is disposed so as to not oppose to the heater unit.