A backlight module unit and a backlight module are provided. The backlight module unit includes a first light source, a second light source, and an optical barrier. A light source interval is defined between the first light source and the second light source, while a barrier interval is defined between the optical barrier and the second light source. Because the barrier interval is substantially shorter than a half of the light source interval, the backlight module unit mixes the light evenly, and prevents the dark bands from forming due to the disposition of the optical barrier. Thereby, the backlight module that comprises the plural aforesaid backlight units will have no dark bands, mix light evenly, and be thin overall.