A liquid feeding system (10, 10A) for a microchip comprising: a flow path having a reaction field (14, 14A) in which is fixed an antibody that reacts specifically with an antigen in an analyte liquid (Lq, 26); a pipette connected to one end side of the flow path; a primary storage section connected to the other end side of the flow path; a pump (130, 24) that reciprocatingly feeds the analyte liquid (Lq, 26) with respect to the reaction field (14, 14A) by applying driving force via a gas to the analyte liquid (Lq, 26) in the pipette; and a control section configured to control the drive of the pump (130, 24); wherein the control section (13 is configured to carry out: a first liquid feeding step of feeding the analyte liquid (Lq, 26) of the pipette via the reaction field (14, 14A) in a direction toward the primary storage section; a second liquid feeding step of feeding the analyte liquid (Lq, 26) in a direction from the primary storage section toward the reaction field (14, 14A), after the first liquid feeding step; and a third liquid feeding step of repeating the feeding of the analyte liquid (Lq, 26) in the direction from the reaction field (14, 14A) toward the primary storage section and the feeding of the analyte liquid (Lq, 26) in the direction from the primary storage section toward the reaction field (14, 14A), after the second liquid feeding step, wherein the control section carries out control of the pump (130, 24) so that a rear gas-liquid interface (gl) of the analyte liquid (Lq, 26) in the first liquid feeding step, and a front gas-liquid interface (gl) and the rear gas-liquid interface (gl) of the analyte liquid (Lq, 26) in the second and the third liquid feeding steps do not pass beyond the reaction field (14, 14A), the liquid feeding system being characterised in that the control section is configured such that the rear gas-liquid interface of the analyte in the first liquid feeding step and the front and rear interfaces in the second liquid feeding step and the third liquid feeding step continue to be positioned above a height of an inside surface of a top wall of the flow path in the reaction field (14, 14A). a flow path having a reaction field (14, 14A) in which is fixed an antibody that reacts specifically with an antigen in an analyte liquid (Lq, 26); a pipette connected to one end side of the flow path; a primary storage section connected to the other end side of the flow path; a pump (130, 24) that reciprocatingly feeds the analyte liquid (Lq, 26) with respect to the reaction field (14, 14A) by applying driving force via a gas to the analyte liquid (Lq, 26) in the pipette; and a control section configured to control the drive of the pump (130, 24); wherein the control section (13 is configured to carry out: a first liquid feeding step of feeding the analyte liquid (Lq, 26) of the pipette via the reaction field (14, 14A) in a direction toward the primary storage section; a second liquid feeding step of feeding the analyte liquid (Lq, 26) in a direction from the primary storage section toward the reaction field (14, 14A), after the first liquid feeding step; and a third liquid feeding step of repeating the feeding of the analyte liquid (Lq, 26) in the direction from the reaction field (14, 14A) toward the primary storage section and the feeding of the analyte liquid (Lq, 26) in the direction from the primary storage section toward the reaction field (14, 14A), after the second liquid feeding step, a first liquid feeding step of feeding the analyte liquid (Lq, 26) of the pipette via the reaction field (14, 14A) in a direction toward the primary storage section; a second liquid feeding step of feeding the analyte liquid (Lq, 26) in a direction from the primary storage section toward the reaction field (14, 14A), after the first liquid feeding step; and a third liquid feeding step of repeating the feeding of the analyte liquid (Lq, 26) in the direction from the reaction field (14, 14A) toward the primary storage section and the feeding of the analyte liquid (Lq, 26) in the direction from the primary storage section toward the reaction field (14, 14A), after the second liquid feeding step, wherein the control section carries out control of the pump (130, 24) so that a rear gas-liquid interface (gl) of the analyte liquid (Lq, 26) in the first liquid feeding step, and a front gas-liquid interface (gl) and the rear gas-liquid interface (gl) of the analyte liquid (Lq, 26) in the second and the third liquid feeding steps do not pass beyond the reaction field (14, 14A), the liquid feeding system being characterised in that the control section is configured such that the rear gas-liquid interface of the analyte in the first liquid feeding step and the front and rear interfaces in the second liquid feeding step and the third liquid feeding step continue to be positioned above a height of an inside surface of a top wall of the flow path in the reaction field (14, 14A).