Understanding complex neural functions of animals, such as "Learning" or "Memory", is very important in biological field. In order to do this, it is necessary to analyze the relationship between neural activity and behavioral changes of animals. Caenorhabditis elegans (C. elegans), is a well-known model animal in neural science, and it is widely used for analysis of the relationship, because it has much simpler neural network compared with other animals. The research objective of visual servo microscope is to observe the specified neuron in C. elegans "while it is moving". This is very difficult because the neuron have to be observed with high magnification objective-lens and the body of C. elegans moves quickly. The neuron easily gets out from the field of view of the microscope. To overcome this problem, we have developed a servo-controlled XY Z stage system to tracks the target. Please note that the target is a neuron in a tiny worm, we have to use high-magnification lens, and the target speed is multiplied by the magnification rate. Thus the apparent target motion is very quick when observed under the microscope. The proposed system has an ability to track the target with a novel template matching algorithm and can also cancel the movement of the target by controlling the XY stage using visual feedback. By applying the proposed system in neuron observation, we have succeeded in recording and in analyzing both of the neural activity and the behavioral changes of C. elegans simultaneously.