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 20 having an accommodation space 200 in which a liquid L to be supplied to outside is accommodated includes a tank body 21 having a mouth part 22 with an opening 23, a cap 25 mounted on the mouth part 22 to close the opening 23, a liquid passage through which the liquid L in the liquid tank 20 flows toward outside, a gas passage 48 having a gap 24 between the mouth part 22 and the cap 25 and a path 41 communicatively connecting to the gap 24 and the accommodation space 200, a liquid flow valve 30 provided on the liquid passage to allow or inhibit a flow of the liquid L to outside, and an aeration valve 45 provided on the gas passage 48 to compensate for a negative pressure occurring in the accommodation space 200.
