A tooth-cleaning device capable of storing or being operatively mounted with an interdental brush includes a floss-pick unit and an interdental-brush unit. The floss-pick unit is provided with a floss-holding portion and a first assembly portion at two opposite ends respectively. The first assembly portion is in communication with an accommodating space in the floss-pick unit. The interdental-brush unit is provided with a second assembly portion and a third assembly portion at two opposite ends respectively. The second assembly portion is protrudingly provided with a bristle section. When the first and second assembly portions are mounted together, the bristle section extends through the first assembly portion to be stored in the accommodating space. Once the first and third assembly portions are mounted together, the bristle section is exposed outside the floss-pick unit. The floss-pick function and interdental-brush function of the tooth-cleaning device can thus be conveniently used.
