The object of the present invention is to provide a micro-reactor, equipped with a high-precision liquid feed system of simple structure, capable of high-precision analysis of at least one item. The present invention provides a micro-reactor for biological substance inspection including a sample storage section, a reagent storage section, a sample pre-processing section, a micro-pump connecting section and a branched minute flow path. And a sample pre-processed by the sample pre-processing section is fed into the minute flow path branched off into at least two parts by a micro-pump and a liquid dividing section, and on the downstream side of each of the branched minute flow paths, the sample is fed to a flow path constituting a reaction site, and then to a flow path constituting the detection site, thereby providing simultaneous measurement of a plurality of items of a sample.