Provided is a capillary tube flow cell used in analyses at very low flow rates and, particularly, in liquid chromatographic analyses. To ensure that high detection sensitivity and low noise can be realized, a flow cell which houses a liquid sample and exposes the liquid sample to radiant light for analysis purposes comprises a capillary tube which has a bent portion for incident light, a bent portion for emergent light and a linear passage of appropriate length formed between the bent portions, a passage portion of the capillary tube being inserted into a slit and the slit being provided with a light pass preventing portion.