This invention describes a method and device for the rapid detection, enumeration and identification of microorganisms. It is based on the production and accumulation of absorbent or fluorescent molecules during reactions between artificial substrates and enzymes in micro-channels of the sampling-detecting unit, which is a part of a sample treating device. The enzymes of cells, or enzymes attached to the cell body through antibody-enzyme conjugates, produce easily detectable concentration of colored or fluorescent molecules in a small volume much faster than in a large volume. Channels that contain microorganisms appear as colored or fluorescent dots when viewed using a light or fluorescent microscope.