Fast microbial detection is accomplished by identifying quantities of microorganisms accurately and easily. A cell 5 is placed on a loading portion. A coherent laser beam source 2 emits laser beam to a cell 5. A CCD area image sensor 4 is an array of light sensitive detectors. An image sensor 4 receives light projection image that passes through a cell 5 illuminated by the beam from a laser beam source 2, generating projection image signals on each light sensitive detectors. The projection image data is fed into a computer and analyzed.