Detection of Neisseria meningitidis, that is one of the most common causes of bacterial meningitis, is being reported, using a micromachined microcalorimeter with a split-flow microchannel structure. The split-flow microchannel scheme constantly keeps the output of the microcalorimeter near zero level when there is no biochemical reaction, which eliminates the need of an active element such as a heater. Thermal components for the microcalorimeter have been fabricated on a high thermal resistivity layer to improve the sensitivity of the device. Using the fabricated sensor, a biological reaction between Neisseria meningitidis group B (NMGB) and a specific monoclonal antibody to its capsular polysaccharide was detected. In order to verify the reliability of the measurement, exactly same number of NMGB was reacted with HmenB3, and optical density was measured by ELISA.