A method for detecting a rare cell having a possibility of being contained in a cell suspension, from the cell suspension by the use of a cell-spreading device , said cell-spreading device comprising: a microchamber chip having, on its surface, two-dimensionally arranged microchambers capable of enclosing and retaining a cell, a channel-forming frame that is united with the microchamber chip so that a channel is formed on the microchambers , an inlet provided in the channel-forming frame in order to allow a cell suspension to flow into the channel , and an outlet provided in the channel-forming frame in order to allow the cell suspension, which has been allowed to flow into the channel through the inlet , to flow out from the channel , wherein the "void ratio" that is a ratio of the sum total of voids to the longitudinal width is not more than 5%, said void being a length obtained by subtracting a width corresponding to a projected aperture of the microchamber from a longitudinal width , the projected aperture of the microchambers being given by projecting the aperture of the microchambers perpendicular to a direction of the longitudinal width of the microchamber chip , said method comprising: a step of introducing the cell suspension into the channel through the inlet of the cell-spreading device to spread cells on the surface of the microchamber chip , and a step of enclosing the spread cells in the microchambers , with a plurality of cycles of an intermittent liquid sending in which the cell suspension is sent through the inlet and thereafter allowed to stand still for a predetermined period of time in one cycle. a microchamber chip having, on its surface, two-dimensionally arranged microchambers capable of enclosing and retaining a cell, a channel-forming frame that is united with the microchamber chip so that a channel is formed on the microchambers , an inlet provided in the channel-forming frame in order to allow a cell suspension to flow into the channel , and an outlet provided in the channel-forming frame in order to allow the cell suspension, which has been allowed to flow into the channel through the inlet , to flow out from the channel , wherein the "void ratio" that is a ratio of the sum total of voids to the longitudinal width is not more than 5%, said void being a length obtained by subtracting a width corresponding to a projected aperture of the microchamber from a longitudinal width , the projected aperture of the microchambers being given by projecting the aperture of the microchambers perpendicular to a direction of the longitudinal width of the microchamber chip , said method comprising: a step of introducing the cell suspension into the channel through the inlet of the cell-spreading device to spread cells on the surface of the microchamber chip , and a step of enclosing the spread cells in the microchambers , with a plurality of cycles of an intermittent liquid sending in which the cell suspension is sent through the inlet and thereafter allowed to stand still for a predetermined period of time in one cycle. a step of introducing the cell suspension into the channel through the inlet of the cell-spreading device to spread cells on the surface of the microchamber chip , and a step of enclosing the spread cells in the microchambers , with a plurality of cycles of an intermittent liquid sending in which the cell suspension is sent through the inlet and thereafter allowed to stand still for a predetermined period of time in one cycle. <EOS>