To provide a flow cell device which is unlikely to have pressure loss or a turblent flow generated, and having a flow channel formed thereto with high precision.

Since the occurrence of the pressure loss or turblent flow of the flow channel as a whole is suppressed because the flow route from a measuring fluid inlet 38 to a discharge port 44 is formed straight, and high measurement precision is obtained. Further, since sheath flow channels 30, a measurement flow channel 32 or the like are constituted, by superposing a first flow channel constituting plate 12 and a second flow channel constituting plate 14, which are divided by a plane passing through the sheath flow channels 30 along the flow direction of a fine flow channel 36, one on the other, they are easily formed with high precision.