A time-lapse embryo image monitoring system consists of an incubator with a built-in microscope and CCD camera. Embryo assessment can be performed with this type of system without removing embryos from the incubator, which eliminates the risks of stress due to temperature changes, light exposure, high oxygen exposure, and pH changes in the culture medium. We cultured embryos to the blastocyst stage using this system and compared the results with those of a normal incubator. We compared the rates of fertilization and cryopreservation of embryos cultured using EmbryoScope^® and a conventional incubator. We then compared the pregnancy rates of EmbryoScope^® and the conventional incubator. We finally examined the relationship between the early cleavage of embryos and blastocyst formation rate. The fertilization rates (EmbryoScope^®: 74.1%, 298/402; conventional incubator: 77.4%, 202/261) and cryopreservation rates (EmbryoScope^®: 57.4%, 163/284; conventional incubator: 48.7%o, 91/187) of embryos were not affected by the incubator. No significant difference was observed in clinical pregnancy rates between the groups: (EmbryoScope^®: 24.5%, 24/98; conventional incubator: 15.0%o, 15/100). The first division time of embryos was significantly faster in the “2-cell” groups (Groups A and B) (P < 0.01) than in the “none 2-cell” group (Group C). The blastocyst formation rates of embryos in Groups A and B were significantly (P < 0.05) higher than those in Group C. These results indicated that EmbryoScope^® enables a detailed and dynamic analysis of the development of human embryos.