Although the microscope is generally used in cell observation, it is not possible to observe cells spread over a wide area collectively as the visual field of a microscope is very narrow. Therefore, we focused on CMOS sensors installed in digital cameras and smartphones, and considered its application in cell observation. A CMOS sensor is a device with tens of millions of fine sensor elements arrayed on it, and the reflections on the sensor can be instantly recorded as images. We developed the technology to collectively detect cells scattered over a wide area by mounting cells directly on a CMOS sensor of a few millimeter square, and recording the image. As this technology does not require a device with an objective lens, such as a microscope, cost reduction and miniaturization of the cell analysis device are possible. Currently, we are developing an HIV diagnosis device based on this technology to be used at environments with poor infrastructure, such as medical institutions and developing countries. Based on this technology, we are also working on an image determining system, which adopts machine learning, for microorganism tests.