Time-lapse video microscopic observation is useful for analysis of cell biology, especially in rapid response of immune cells. Dendritic cells (DCs) have multiple functions in the immune system, and DCs in peripheral blood play an especially important role at the front line of infection. We have developed a time-lapse video microscopic method for the evaluation of single myeloid DCs (MDC-1) from human peripheral blood. MDC-1 displayed generalized plasma membrane ruffling and phagocytosis of Pseudomonas aeruginosa. The morphological changes of MDC-1 increased following stimulation with P. aeruginosa but not after stimulation with supernatant from a P. aeruginosa culture. The activation of these morphological changes in MDC-1 could be quantitatively analyzed using the time-lapse video microscopy. This novel system may be useful for the evaluation of rapid response with human immune cells against bacterial infection.