A liquid tank capable of preventing a gas passage from being clogged and a dental device including this liquid tank are provided. A liquid tank having an accommodation space in which a liquid L to be supplied to outside is accommodated includes a tank body having a mouth part with an opening, a cap mounted on the mouth part to close the opening, a liquid passage through which the liquid L in the liquid tank flows toward outside, a gas passage having a gap between the mouth part and the cap and a path communicatively connecting to the gap and the accommodation space, a liquid flow valve provided on the liquid passage to allow or inhibit a flow of the liquid L to outside, and an aeration valve provided on the gas passage to compensate for a negative pressure occurring in the accommodation space.
