Fusarium crown and root rot of tomato was caused by a pathogenic fungus, Fusarium oxyspoum f. sp. radicis-lycopersici (FORL), and the outbreak of this disease has occurred frequently throughout the world since 1970’s. Although many researches were reported in Fusarium disease of tomato or other crops, the mechanisms of pathogenicity and symptom induction are poorly understood. In actual soil culture or hydroponics, it was not easy to understand the behavior of pathogen or induction of disease symptoms on inoculated roots under ground. To solve this problem, we established an easily handleable method for monitoring of symptomatic events in plants inoculated with FORL. The cotyledon-stage seedlings grown on filter paper-wrapped glass slides slanted in the culture bottle were inoculated by dropping conidial suspension onto the roots. The symptomatic data of seedlings inoculated with 13 isolates of FORL was recorded and evaluated on the basis of the frequency and rapidity of the disease symptoms (such as root browning, crown rotting and wilting) using special analytic software. Using this system, we found localization of early symptoms on inoculated roots, and describe the critical difference in disease progress between the isolates of FORL with different levels of pathogenicity.