Abstract: A microchip, which is used in a diagnostic system using a microfluid system, has a flow path capable of greatly improving the reaction efficiency and realizing a stable measurement with high reproducibility. The microchip has two substrates with at least a flow path 12 formed at the interface between the two substrates, the flow path 12 having a reaction area 14 and a detection area 15 downstream of the reaction area 14, and the flow path 12 at the detection area 15 having a depth which is deeper than the flow path 12 in the reaction area 14.

Abstract: The invention provides an analytical device insusceptible to inactivation or other influences even when exposed to a thermal load or organic compounds contained in an adhesive in the process for manufacturing the same and, more over, allowing an immunological substance or the like to be readily immobilized at a site in the microchannel passage therein. The analytical kit is a combination of the analytical device and a reagent or reagents. The analytical device used in the analytical kit comprises a passage 2, 1 ?m-5mm width and 1 ?m-750 ?m depth in cross-section formed therein and belongs to the category of the so-called microfluidic systems suited for analyzing very small amounts of liquid samples; thus, it is suited for analyzing biological substances.